whitecap n.

Old English hwit "bright, radiant; clear, fair," also as a noun (see separate entry), from Proto-Germanic *hweit- (source also of Old Saxon and Old Frisian hwit, Old Norse hvitr, Dutch wit, Old High German hwiz, German weiß, Gothic hveits), from PIE *kweid-o-, suffixed form of root *kweit- "white; to shine" (source also of Sanskrit svetah "white;" Old Church Slavonic sviteti "to shine," svetu "light;" Lithuanian šviesti "to shine," švaityti "to brighten").

As a surname, originally with reference to fair hair or complexion, it is one of the oldest in English, being well-established before the Conquest. Meaning "morally pure" was in Old English. Association with royalist causes is late 18c. Slang sense of "honorable, fair" is 1877, American English; in Middle English it meant "gracious, friendly, favorable." The racial sense "of those races (chiefly European or of European extraction) characterized by light complexion" is recorded from c. 1600; meaning "characteristic of or pertaining to white people" is from 1852, American English. White supremacy attested from 1868, American English [John H. Van Evrie, M.D., "White Supremacy and Negro Subordination," New York, 1868]; white flight is from 1966, American English.

White way "brightly illuminated street in a big city" is from 1908. White flag of truce or surrender is from c. 1600. White lie is attested from 1741. White Christmas is attested from 1847. White House as the name of the U.S. presidential residence is recorded from 1811. White water "river rapids" is recorded from 1580s. White Russian "language of Byelorussia" is recorded from 1850; the mixed drink is from c. 1978. Astronomical white dwarf is from 1924. White witch, one who used the power for good, is from 1620s.

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.