late 16c., "one who whips or scourges himself for religious discipline," from Latin flagellantem (nominative flagellans), present participle of flagellare "to scourge, lash" (see flagellum). There were notable outbreaks of it in 1260 and 1340s. As an adjective, "given to flagellation," 1880.[flagellant etymology, flagellant origin, 英语词源]