late 15c., from French béguine (13c.), Medieval Latin beguina, "a member of a women's spiritual order professing poverty and self-denial, founded c. 1180 in Liege in the Low Countries." They are said to take their name from the surname of Lambert le Bègue "Lambert the Stammerer," a Liege priest who was instrumental in their founding, and it's likely the word was pejorative at first. French bègue is of unknown origin. Related: Beguinage.
The women's order, though sometimes persecuted, generally preserved its good reputation, but it quickly drew imposters who did not; nonetheless it eventually was condemned as heretical. A male order, called Beghards founded communities by the 1220s in imitation of them, but they soon degenerated (compare Old French beguin "(male) Beguin," also "hypocrite") and wandered begging in the guise of religion; they likely were the source of the words beg and beggar, though there is disagreement over whether Beghard produced Middle Dutch beggaert "mendicant" or was produced by it. The male order was condemned by the Church early 14c. and vanished by mid-16c.
Cole Porter's "Begin the Beguine" (1935) refers to a kind of popular dance of West Indian origin, from French colloquial béguin "an infatuation, boyfriend, girlfriend," earlier "child's bonnet," and before that "nun's headdress" (14c.), from Middle Dutch beggaert, ultimately the same word as the above. Compare English biggin "child's cap" (1520s), from the French word.
1900, coined by U.S. author L. Frank Baum (1856-1919) in "The Wonderful Wizard of Oz." He never explained how he got the word.
The word most like it is perhaps mutchkin, an old Scottish measure of capacity for liquids, which was used by Scott. (It comes from Middle Dutch mutseken, originally "a little cap," from mutse "cap," earlier almutse "amice, hood, headdress," from Latin amictus "mantle, cloak," noun use of past participle of amicire "to wrap, throw around," a compound from ambi- "around" (see ambi-) + iacere "to throw" (see jet (v.)).
But some Baum scholars see a possible inspiration in Münchner Kindl, the name of the emblem of the city of Munich (German München) or in German Männchen, literally "little man," which is cognate with mannequin.
While she stood looking at the strange and beautiful sights, she noticed coming toward her a group of the queerest people she had ever seen. They were not as big as the grown folk she had always been used to; but neither were they very small. In fact, they seemed about as tall as Dorothy, who was a well-grown child for her age, although they were, so far as looks go, many years older. ["The Wonderful Wizard of Oz"]
late Old English cæppe "hood, head-covering, cape," a general Germanic borrowing (compare Old Frisian and Middle Dutch kappe, Old High German chappa) from Late Latin cappa "a cape, hooded cloak" (source of Spanish capa, Old North French cape, French chape), a word of uncertain origin. Possibly a shortened from capitulare "headdress," from Latin caput "head" (from PIE root *kaput- "head").
The Late Latin word apparently originally meant "a woman's head-covering," but the sense was transferred to "hood of a cloak," then to "cloak" itself, though the various senses co-existed. Old English took in two forms of the Late Latin word, one meaning "head-covering," the other "ecclesiastical dress" (see cape (n.1)). In most Romance languages, a diminutive of Late Latin cappa has become the usual word for "head-covering" (such as French chapeau).
The meaning "soft, small, close-fitted head covering" in English is from early 13c., originally for women; extended to men late 14c.; extended to cap-like coverings on the ends of anything (as in hubcap) from mid-15c. The meaning "contraceptive device" is by 1916.
The meaning "cap-shaped piece of copper lined with gunpowder and used to ignite a firearm" is by 1825, hence cap-gun (1855); extended to paper strips used in toy pistols by 1872 (cap-pistol is from 1879).
Figurative thinking cap is from 1839 (considering cap is 1650s). Cap and bells (1781) was the insignia of a fool; cap and gown (1732) of a scholar. To set one's cap at or for (1773) means "use measures to gain the regard or affection of," usually in reference to a woman seeking a man's courtship.