c. 1500, "trooper, dragoon, horse-soldier," from Old French routier "a highwayman," also "experienced soldier," a word taken into Old French from Medieval Latin ruptarius, rutarius, a name for a band of irregular soldiers or mercenaries, from Vulgar Latin rupta "a dispersed group," literally "a broken group," from noun use of Latin rupta, fem. past participle of rumpere "to break" (see rupture (n.)).
The French word also is the source of Dutch ruiter, German Reuter "trooper, horseman." In French partly conformed to route, and in German to Reiter "rider;" Ritter "knight." Related: Rutterkin "swaggering gallant, bully" (1520s).