1570s, "customer," short for obsolete chapman in its secondary sense "purchaser, trader" (also see cheap). The colloquial familiar sense of "lad, fellow, man or boy" is first attested 1716, usually with a qualifying adjective. Compare slang (tough) customer and German Kunde "customer, purchaser," colloquially "fellow."

"to crack open in fissures," mid-15c., chappen (intransitive) "to split, burst open in fissures;" "cause to split or crack" (transitive); perhaps a variant of choppen (see chop (v.), and compare strap/strop), or related to Middle Dutch kappen "to chop, cut," Danish kappe, Swedish kappa "to cut."

Usually in reference to the effects of extreme cold followed by heat on exposed body parts. Related: Chapped; chapping. The noun meaning "fissure in the skin" is from late 14c.

also chapbook, 1812, from chap, short for chapman, so called because chapmen once sold such books.

One of a class of tracts upon homely and miscellaneous subjects which at one time formed the chief popular literature of Great Britain and the American colonies. They consisted of lives of heroes, martyrs, and wonderful personages, stories of roguery and broad humor, of giants, ghosts, witches, and dreams, histories in verse, songs and ballads, theological tracts, etc. They emanated principally from the provincial press, and were hawked about the country by chapmen or peddlers. [Century Dictionary] 

"jaws, cheeks," from chap (n.), 1550s, which is of unknown origin. Hence, chap-fallen "with the lower jaw hanging down" (1590s), hence, figuratively, "dejected, disspirited" (c. 1600).

"man, person, fellow, chap," canting slang from at least 1560s, said to be from Romany (Gypsy) cova "a thing," covo "that man" [Barrère and Leland].

early 15c., "one who shaves or cuts hair," agent noun from shave (v.); sense of "fellow, chap" is slang from 1590s. Meaning "shaving tool" is from 1550s (as a kind of medical instrument, early 15c.). Mad shaver (1610s) was 17c. slang for "a swashbuckler, roisterer."

mountain range between the Black and Caspian seas, separating Europe and the Middle East, from Latin Caucasus, from Greek kaukasis, said by Pliny ("Natural History," book six, chap. XVII) to be from a Scythian word similar to kroy-khasis, literally "(the mountain) ice-shining, white with snow." But possibly from a Pelasgian root *kau- meaning "mountain."

"one engaged in the business of buying commercial commodities and selling them again for profit," early 13c., marchaunt (late 12c. as a surname), from Anglo-French marchaunt "merchant, shopkeeper" (Old French marcheant, Modern French marchand), from Vulgar Latin *mercatantem (nominative *mercatans) "a buyer," present participle of *mercatare, frequentative of Latin mercari "to trade, traffic, deal in" (see market (n.)). Meaning "fellow, chap" is from 1540s; with a specific qualifier, and suggesting someone who deals in it (such as speed merchant "one who enjoys fast driving," by 1914).

"sodomite," 1550s, earlier "heretic" (mid-14c.), from Medieval Latin Bulgarus "a Bulgarian" (see Bulgaria), so called from bigoted notions of the sex lives of Eastern Orthodox Christians or of the sect of heretics that was prominent there 11c. Compare Old French bougre "Bulgarian," also "heretic; sodomite."

The softened secondary sense of "fellow, chap," is in British English "low language" [OED] from mid-19c. The meaning "something unpleasant, a nuisance" is from 1936. Related: Buggerly.

The religious heretics in question were the Bogomils, whose name is a Slavic compound meaning "dear to God" (compare Russian bog "god") and might be a translation of Greek theophilos.

1729, "jester, merry fellow, one who jokes," agent noun from joke (v.). In generic slang use for "any man, fellow, chap" by 1811, which probably is the source of the meaning "odd face card in the deck" (1868), also often jolly joker. An 1857 edition of Hoyle's "Games" lists a card game called Black Joke in which all face cards were called jokers.

American manufacturers of playing-cards are wont to include a blank card at the top of the pack; and it is, alas! true that some thrifty person suggested that the card should not be wasted. This was the origin of the joker. ["St. James's Gazette," 1894]