The noun ‘easel’ was borrowed from Dutch ‘ezel’; this sense of ‘ezel’ is a metaphorical extension of its literal meaning, ‘ass’, from the fact that, like a beast of burden, an easel is used to carry things. Likewise, the literal meaning of the synonymous French word ‘chevalet’ is ‘little horse’.
The noun easel denotes a wooden frame for holding an artist’s work while it is being painted or drawn.
It is first recorded in The mysteryes of nature, and art: conteined in foure severall treatises (London, 1634), an illustrated book on waterworks and hydraulic machinery, also including sections on drawing, painting, recipes, folk remedies, as well as one on fireworks and incendiary devices, by John Bate (floruit 1626-35).
First provide a frame or Easel called by Artists, which is very necessary to worke upon, especially in greater pieces of worke: the forme whereof followeth.
The word easel was borrowed from Dutch ezel, which is attested in its earlier form esel and in the sense of easel in Etymologicum teutonicæ linguæ: sive dictionarium teutonico-latinum (Antwerp, 1599), by Cornelis Kiliaan (1528-1607); this word was introduced into Britain among other painting terms under the influence of 16th– and 17th-centuries Dutch art.
This sense of ezel is a metaphorical extension of its literal meaning, ass, from the fact that, like a beast of burden, an easel is used to carry things.
Similarly, horse is used to designate a frame or structure, often having legs, on which something is mounted or supported*; for example, the following definition is from Cyclopædia: or, an universal dictionary of arts and sciences (London, 1728), by Ephraim Chambers (circa 1680-1740):
Horse, is also a Term used in various of the Arts and Manufactories, for something that helps to sustain their Work from the Ground, for the more commodious working at it.
(* cf. also a horse that was foaled of an acorn, i.e., the gibbet)
And, in An Universal Dictionary of the Marine (London, 1769), the poet and lexicographer William Falconer (1732-70) translated French baudet as:
a sawyer’s frame, horse, or tresle [= trestle].
The literal meaning of baudet is ass. Likewise, easel translates in French as chevalet, literally little horse, a diminutive of cheval, horse; in A Dictionarie of the French and English Tongues (1611), Randle Cotgrave defined chevalet as:
A Nagge, or little horse; also, the Bridge of a Lute, Violl, &c.; also, the woodden logge whereon a Tanner scrapes his hides; (wee call it, his beame;) also, a sawing tressle; also, a kind of racke, or stretching torture.
(The rack was an instrument of torture consisting of a frame on which the victim was stretched by turning rollers to which the wrists and ankles were tied.)
The sense painter’s easel of chevalet is first recorded in Dictionnaire françois (Geneva, 1680), by Pierre Richelet (1626-98).
Similarly, in the other Romance languages, easel translates as:
– caballete in Spanish; it is a diminutive of caballo, horse;
– cavalete in Portuguese; from cavalo;
– cavallet in Catalan; from cavall;
– cavalletto in Italian; from cavallo.
But the Romanian word is şevalet, a calque of French chevalet (ş transcribes the sound /ʃ/ as in English shine).