In Greek sophrosyne, in Latin temperantia is one of the four cardinal virtues. As Plato explains in the Republic, it controls the concupiscent appetite and it essentially consists, as Aristotle makes clear in Nicomachea Ethics, of a moderation of sensitive pleasures in compliance with the requirements of the “straight reason”. Saint Thomas in the Summa Theologiae writes “Temperance that implies moderation, mainly consists in regulating the passions that stretch to the sensitive goods, and that are concupiscence and pleasures, and indirectly regulating sadness and pains that derive from the absence of these pleasures” (quaestio 2, articulum 2). The moderating person is therefore the one that is strained to resist to the attraction of passions and pleasures, in particular sensual ones, when they become excessive.
In the XVIth Sermones de Ludo Temperance is just put close to Love as a virtue that teaches the moderation of  instincts.
Temperance is generally represented in illuminated tarots (figure 1 - Visconti Sforza Tarot / figure 2 - Charles VI Tarot) in its more common version: a young girl in the action of pouring water from a container into another containing wine, which is meant to mitigate, to dampen what is too exciting. It expresses therefore the necessity to dominate certain instincts, that, through this virtue, they become balanced.
An iconographic variant of remarkable interest appears in Alessandro Sforza’s Tarot (figure 3). A nude woman is seated on the back of a deer, turning her shoulders towards the head of the animal. With her right hand she pours water from a cup making the liquid fall on her sex, which she covers with her left hand (figure 4). The cup seems to be less striking, as it has been impressed by  punching together with other decorative elements (figure 5). It is a particular representation of Temperance: a fable about ancient gods used as moral training, in accordance with the typical praxis of the time.
It is now necessary to emphasize the function that the “ancient gods” myths had in the medieval ages, in relation to the Christian allegory. Fundamental to this are the studies of Jean Seznec who in his work The Survival of the Ancient Gods writes: “Mythology stretched to transform into a moral philosophy: and Philosophia moralis is not by chance the title of a work of the eleventh century, attributed to Ildeberto of Lavardin, bishop of Tours, which brings numerous examples of allegorical interpretation taken from pagan poets as well as from the Bible. But at the same time mythology stretched to also fuse with theology: as well as, renewing the tradition of the Fathers, the medieval allegorical genius discovered in the personages and in the episodes of the Old Testament forecasts of the New Alliance, in the same way that it discovered in the personages and the episodes of mythology forecasts of the Christian Truth.
Really, starting from the twelfth century, in which allegory assumes the function of a universal vehicle of every manifestation of religious “pietas” (Pity), the mythological interpretation comes to an amazing development. This is in fact the age in which Alexander Neckham connects gods of paganism with the virtues that, according to Saint Augustin, lead man to the Saint Christian detection; the age in which Guglielmo of Conches, commenting in the De consolatione philosophiae by Boezio, discovers in Euridice a symbol of the inner concupiscence of the human heart, and in the war of the Giants against Zeus the rebellion of our bodies made with mud against the spirit; and still the age in which Bernardo of Chartres and his disciple Giovanni of Salisbury put the pagan polytheism at the centre of their own meditation, "not to respect its false divinities, but because they hide mysterious instructions inaccessible to common people. But above all this is the age in which the Metamorphosis of Ovid profuse to sagacious interpreters unsuspicious treasures of saint truth” (1990, page 122).
According to the Christian meaning, Temperance has the task of taming in a principalled way, sensuality and sexual pleasures, and so between the virtues and connected to it there is Chastity. In the Tabernacolo by the Orcagna (Florence, Orsammichele) the four cardinal virtues are represented, each one placed side by side with the connected virtues, according to Saint Thomas precepts; in particular, Humility and Virginity are connected to Temperance.
The representation in Alessandro Sforza’s card is connected to the Greek myth of Diane, that rises as a moral training allegory. The goddess, during the recurrence of the Anados, her annual apparition, a moment in which she renewed her virginity bathing in a sacred source, was watched and wished with concupiscence by Atteone. Furious, the goddess changed him into a deer (figure 6 - Ceramic Plate, ca.1535. International Museum of the Ceramics, Faenza) an animal directly connected to her myth as goddess of hunting, that was called “elafebòlos”, that means deer darter. But the deer was also considered as an animal symbolic of mildness and provided with many qualities. In the Tuscany Bestiary Libro sulla natura degli animali (Book of the nature of the animals) a medieval moral essay, the Christian is repeatedly invited, through opportune animal examples, to exercise the virtues demanded by his profession of faith and to the constant practice of confession and penance. This work tells of how the deer was able to kill the snakes, in order then to eat them and to get rid of the ingested poison drinking pure water. From this behaviour there is a precept of moral training “Also men must imitate it, getting rid of hatred, of lust, of rage, of the avarice resorting to the alive source, that is Christ” (Chapter XLVI).
In the myth Diane is always a virgin goddess: her constant ritual is the gesture to reach and to pour water, element of regeneration and purification. For this reason in Rome the vestal virgin temples were built between small woods in proximity of sources gushing from cliffs. Diana completes hers ritual of purification in order not to dampen eventual ardours (since the goddess is always virgin) but pouring water in her “water” (her sex, as container connected to liquids) she’s in contact with energies of the two waters, renewing her virginal purity.
Being based on the described myth the representation assumes a moral worth: as Diana has prevailed on Atteone, symbol of temptation and she has made him mild, in the same way men must tame and submit instincts, maintaining chastity drawing from the holy water of Temperance.
The position assumed by the Goddess over the deer is not unusual in the late medieval art. In a Venice mortar of the XV century a fantastic animal is mounted by a putto exactly in the same way (figure 7), while in a capital of the Ducal Building in Venice we find a similar attitude in the fourteenth-century astrological representation of The Sun on the Lion (figure 8). Such composing typology, set to affirm a complete dominion upon the ridden being, as we find even in the card of Strength in the Tarot of Yale (figure 9), has its origin in the representations by Aristotle and Phyllis of which exists ample documentation in Middle Ages and the Renaissance art (figura 10: Memmo di Filippuccio, documented from 1288 to 1324, The Profane Love, detail with Aristotle and Phyllis, fresco. Civic Museum, San Gimignano - Figure 11: Francesco di Antonio del Chierico, The Triumph of Love, by Petrarca, detail with Aristotle and Phyllis, ms. Ital. 545, 1546. Bibliothèque Nationale, Paris).
In the card of the so-called Mantegna Tarots an ermine appears at the feet of the young girl (figure 12). The Ripa in his essay of iconology writes that in order to represent this virtue: “si puo ancora dipingere l’ermellino, per la gran cura che ha di non imbrattare la sua bianchezza, simile a quella di una persona casta” (It is still possible to paint the ermine, for the great care it takes to not smear its whiteness, similar to that of a chaste person) (page 102, ed. 1613).
The jurist Andrea Alciati, the famous author of the Emblemata in another of his works, the Parergon Juris appeared for the first time in 1538, in Chapter XVI named De ludis nostri temporis puts Fame to represent Temperance:

Mundus habet primas, croceas dein Angelus alis:
Tum Phoebus, luna, & stellæ, cum fulmine dæmon:
Fama necem, Crux ante senem, fortuna quadrigas:
Cedit amor forti & justo: regemque sacerdos,
Flaminicam (1) regina præit que is campo propinat
Omnibus: extremo stultus discernitur actu.

The world has the primate, then the golden winged angel;
Then Phoebus, the moon and the stars, the devil with the lightening;
Fame precedes death, the cross the old man, fortune the chariot;
Love gives up to the strong and justice, the priest precedes the king,
The queen precedes the high priest’s wife, the innkeeper offers drinks
To all these ones, at last the fool is recognizable by his behavior.

(1) The flaminica was a priestess of Jupiter, wife of a flamen (priest), one of the higher religious offices in ancient Rome. Here for High Priestess.

Obviously, this isn’t a personal nature variation, but a replacement in perfect harmony with the earth prerogative of Temperance, which is to make known, through virtuous deeds, the temperate man, according to a concept expressed by the Fathers of Church and  the Ancients.
Pierre de La Primaudaye in the first volume of his work  Académie française, divisée en dix-huit journées [traitant] de l'institution des mœurs, et de ce qui concerne le bien et heureusement vivre en tous états et conditions, par les préceptes de la doctrine et les exemples de la vie des anciens sages et hommes illustres  (Cinquieme iournee “De la Temperance”, Chap. XVII) dated to 1577, about the four parts of Temperance writes: “O combien (dit Euripide) la Temperance est a estimer, veu qu’elle produit entre les hommes tant de gloire & d’honneurs. Ceste vertu est devisee en quatre principales parties, Continence, Clemence, Modestie, & Ordre……..La Modestie, par laquelle l’honneste honte & pudeur peut acquesir une bonne & bien meritee renomee”.
A joint concept on Temperance, which makes the man famous, is expressed by Giovanni B. Bovio in  Teatro morale dogmatico-istorico dottrinale e predicabile nel quale si spiegano le Virtù, ed i Vizi, coll’autorità della Sagra Scrittura, de’ Santi Padri, con Ragioni, Similitudini, ed Esempi: "Whenever people will see in their society temperate men, who hate the gluttony, debauchery, and other detestable waste of time, lovers and practitioners of Temperance with so much prudence, will consider them very much, in accordance and in honor. People will see in them the ornaments and objects that give fame and reputation to their country” (Second Volume, Rome, 1734, pag. 58)
In Etteilla cards (Grand Etteilla II) Temperance is represented as a child who has a bite on her hand, with the obvious symbolic function of refraining the ardours, and by an elephant, also a symbol of chastity (figure 13) as it appears in the figure of Temperance in the Ripa essay (figure 14). About this concept he writes: “L’ elefante è posto per la Temperanza, perche essendo assuefatto da una certa quantita di cibo non vuol mai passare il solito, prendendo solo tanto, quanto è sua usanza per cibarsi" (The elephant is placed for Temperance, as being accustomed to a certain quantity of food it never wants more than usual, just taking as much as it is used to in order to feed itself” (page 297, ed. 1613).