1690s, "aggressive, boisterous," a Scottish word of uncertain origin, probably from rand "to rave," an obsolete variant of rant (v.). "In early use always of beggars, and probably implying vagrant habits as well as rude behavior. Now applied only to women" [OED]. The sense of "lewd, lustful, noisily wanton" is attested by 1847. Compare Scottish and northern English randy (n.) "a sturdy beggar or vagrant" (of males); "a noisy hoyden, a rude, romping girl." Related: Randiness.