Stemming from medieval traditions inspired by Celtic mythology, she first appeared in The Grand and Priceless Chronicles of the Great and Enormous Giant Gargantua, written in 1532, in which Merlin created her from bones atop a mountain.

Incidents include the mare drowning her enemies with her urine and levelling all the trees of Beauce, transforming the region into a plain.

As seen in two major Renaissance literary works, the Great Mare likely arose from popular traditional stories and ancient oral folklore.

According to Dontenville, the mare and its rider were mistakenly taken for a dragon, as is attested in the etymology of "G-R-G", a reference found in the names of the Giants of Rabelais (Grandgousier, Gargamelle and Gargantua).

The legend of "The Great Mare" and other similar tales of white horses are present in French beliefs and toponymes related to the west coast sea.

[6][7] In Paul Sébillot's collections of popular traditions it is written that the sea in Poitou is referred to as "the Great White Mare".

[9] In addition to this, off the coast of Ouessant there exists La Jument lighthouse built on the Ar Gazec reef ("the mare" in Breton).

He wrote that he believed the existence of these toponymes and the city they belonged to inspired Rabelais to write the arrival of the Great Mare.

[10] According to the French mythological society, this Great Mare made gigantic imprints that can still be seen in modern day, one within the Jura mountains, and the second in Normandie.

[4] The mare's tail then turned into a ax[19] and following this, Gargantua then hung the bells of the Notre-Dame de Paris cathedaral[19] around her neck.

[21] This scene borrowed the concept of the flight of the Notre-Dame bells, which the giant hung around the neck of his mare[20] (however, under Rabelais' pen script the passage takes on a new dimension by approaching the themes of culture, politics, morals, religion and aesthetics[15]).

In the aforementioned chapter XVI, the mare is given a tone in the fable that marks a break in the ambience of the story[21] into a more popular and less academic burlesque.

"Rabelais sets aside supernatural elements, in a very distinct manner than The Chronicles or The Four Aymon Sons, in order for this chapter's background to evoke the concerns of peasants and city dwellers, and therefore emphasize the relationship between man and nature.

[21] Claude Gaignebet, in contrast, compares the Grand Mare to the Bayard horse of the Song of the Four Aymon Sons, saying that she is a magical creature that stemmed from popular folklore in connection with the alchemical and erudite tradition, as a result of her creator, Merlin.

[24] Other ancient theories perceived the source of the Grand Mare's inspiration as possibly being Diane de Poitiers, nicknamed "The Great Seneschal" from Rabelais' time.

Her size was that of "six elephants",[27][13] she had the hanging ears of a Languedoc goat, with her "feet split into fingers like Jules César's horse[21] [...] and a small horn on the flank".

Hence it is said that is how Beauce got its name,[30][16][20] Gargantua takes obvious joy from seeing the rampaging damage from his mount, but is careful not to expressly show the emotion, a reaction that is meant to give the reader the impression that he is an adolescent.