early 15c., "the dodging movements of a hunted animal" (a sense now obsolete); 1620s as "a trick, a stratagem, an artifice," from Old French ruse, reuse "diversion, switch in flight; trick, jest" (14c.), a noun from reuser "to dodge, repel, retreat; deceive, cheat," which is from Latin recusare "make an objection against; decline, refuse, reject; be reluctant to" (see recuse; also compare rush (v.)).
It also has been proposed that the French word may be from Latin rursus "backwards," or a Vulgar Latin form of refusare. Johnson calls it, "A French word neither elegant nor necessary."
The verb ruse was in Middle English (rusen), mid-14c. as "drive (someone) back in battle," also "retreat, give ground, withdraw;" late 14c., of game animals "travel so as to elude pursuit." The noun also was used in Middle English in the sense of "roundabout course taken by a hunter in pursuit of prey."