"knavish deeds," 1520s, from knave + -ery.

late 14c., "low, vulgar," from knave + -ish. Meaning "rascally" is from late 15c. (implied in knavishly). Related: Knavishness.

c. 1300, ladde "foot soldier," also "young male servant; man of low social position, vagabond" (attested as a surname from late 12c.), possibly from a Scandinavian language (compare Norwegian -ladd, in compounds for "young man"), but of obscure origin in any case.

The meaning "boy, youth, young man" is from mid-15c.

Liberman (2008) derives it from Old Norse ladd "hose; woolen stocking." "The development must have been from 'stocking,' 'foolish youth' to 'youngster of inferior status' and (with an ameliorated meaning) to 'young fellow.'" He adds, "Words for socks, stockings, and shoes seem to have been current as terms of abuse for and nicknames of fools."

In modern use often familiar or affectionate, in Middle English an insult or term of contempt, e.g. "Where has þou bene so long fro me, Vyle stynkand lad?" in the Towneley mystery plays, also 15c. phrase "(to know) a lord from a lad."

For connection of "youth" and "servant" compare knave. Related: Ladage "boyhood."

also moustache (chiefly British), "the hair that grows upon the upper lip of men," 1580s, from French moustache (15c.), from Italian mostaccio, from Medieval Greek moustakion, diminutive of Doric mystax (genitive mystakos) "upper lip, mustache," related to mastax "jaws, mouth," literally "that with which one chews" (perhaps from PIE root *mendh- "to chew;" see mandible), but Beekes says this whole group of Greek words may be of Pre-Greek origin.

Borrowed earlier (1550s) as mostacchi, from the Italian word or its Spanish derivative mostacho. The plural form of this, mustachios, lingers in English (the mustache sometimes was considered as the hair on either side of the lip, hence the use of the plural form). Slang shortening stache attested from 1985. Old English had cenep "mustache," which is related to cnafa "boy" (see knave). Mustache-cup, one with a fixed cover over part of its top, allowing one to drink without dipping the mustache, is by 1868.

Middle English spelling of a common Germanic consonant-cluster (in Old English it was graphed as cn-; see K). The sound it represented persists in most of the sister languages, but in English it was reduced to "n-" in standard pronunciation by 1750, after about a century of weakening and fading. It was fully voiced in Old and Middle English.