lad: [13] Lad originally meant ‘male of low status or social rank’, and hence ‘male servant’, but by the 14th century its progression to the presentday ‘young male’ was well under way. It is not known where it came from, but there seems to be a strong likelihood of a Scandinavian origin (Norwegian has -ladd in compounds referring to ‘(male) persons’).
lad (n.)
c. 1300, ladde "foot soldier," also "young male servant" (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. OED hazards a guess on Middle English ladde, plural of the past participle of lead (v.), thus "one who is led" (by a lord). Liberman 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." Meaning "boy, youth, young man" is from mid-15c. Scottish form laddie, a term of endearment, attested from 1540s.