1510s, "to dance, frolic," from Middle English adjective frisk "lively" (mid-15c.), from Middle French frisque "lively, brisk," in Old French "fresh, new; merry, animated" (13c.), which is possibly from a Germanic source (compare Middle Dutch vrisch "fresh," Old High German frisc "lively;" see fresh (adj.1)). Sense of "pat down in a search" first recorded 1781. Related: Frisked; frisking. As a noun, "a frolic, gambol," from 1520s.