mid-15c., apparently imitative of forcible exhaling. Extended sense of "to bluster with arrogance or indignation" is attested from 1590s. Related: Huffed; huffing. As a slang term for a type of narcotics abuse, by 1996. Huff cap was 17c. slang for "swaggerer, blusterer" (i.e., one with an inflated head), and was noted in 1577 among the popular terms for "strong beer or ale" (with mad dog and dragon's milk), probably because it goes to the head and huffs one's cap.

also night-cap, late 14c., "covering for the head, worn in bed," from night + cap (n.). In the alcoholic sense, it is attested from 1818. American English sense of "final event in a sporting contest" (especially the second game of a baseball double-header) is by 1924.

Sunday's baseball opening brought out New York vs. Cleveland in the first game. with Philadelphia and Cincinnati as the star attraction in the nightcap number. [The Typographical Journal, September 1923]

1776, "extra duties of a soldier," from fatigue (n.). As a military clothing outfit, from 1836, short for fatigue dress (1833); fatigue cap is from 1824.

square cap worn by Catholic clergy, 1590s, from Italian beretta, from Late Latin birrus, birrum "large cloak with hood;" which is perhaps of Gaulish origin, or from Greek pyrros "flame-colored, yellow."

1660s, "round, approximately flat surface," from Latin discus "quoit, discus, disk," from Greek diskos "disk, quoit, platter," related to dikein "to throw" (see discus).

The American English preferred spelling; also see disc. From 1803 as "thin, circular plate;" sense of "phonograph disk" is by 1888; computing sense is from 1947. Disk jockey first recorded 1941; dee-jay is from 1955; DJ is by 1961; video version veejay is from 1982. Disk-drive is from 1952.

mid-15c., coifen, "to cover with a cap," from Old French coifier, from Old French coife (see coif (n.)); sense of "to arrange the hair" is attested in English from 1835. Related: Coifed; coifing.

1580s, noun ("person who acts madly or wildly") and adjective ("wild, harum-scarum), from mad (adj.) + cap, used here figuratively for "head." Related: Madcappery. Compare mad-brain "rash or hot-headed person" (1560s).

1660s, of birds, from white (adj.) + cap (n.). Attested from 1773 in reference to breaking waves, from 1818 of mushrooms, and from 1891 in reference to "one of a self-constituted band in U.S. who committed outrages under pretense of regulating public morals" [OED].

also jock-strap, "supporter of the male genital organs, used in sports," 1887, with strap (n.) + jock slang for "penis" c. 1650-c. 1850, probably one of the many colloquial uses of Jock (the northern and Scottish form of Jack), which was used generically for "common man" from c. 1500. Jockey-strap in the same sense is from 1890, with also an example from 1870 but the sense is uncertain.

"knee cap, small movable bone in front of the knee-joint," 1690s, from Latin patella "small pan or dish; kneecap," diminutive of patina "pan" (see pan (n.)). So called from its shape. Earlier in Englished form patel (1570s). Related: Patellar; patelliform.