Is it ensure, insure, or assure?
1775, "portable firearm having a spirally grooved bore," used earlier of the grooves themselves (1751), noun use of rifled (pistol), 1680s, from verb meaning "to cut spiral grooves in" (a gun barrel); see rifle (v.2).
"to plunder," early 14c. (implied in rifling), from Old French rifler "strip, filch, plunder, peel off (skin or bark), fleece," literally "to graze, scratch" (12c.), probably from a Germanic source (cf. Old English geriflian "to wrinkle," Old High German riffilon "to tear by rubbing," Old Norse rifa "to tear, break"). Related: Rifled; rifling.
"to cut spiral grooves in" (a gun barrel), 1630s, probably from French rifler, from Old French rifler "to scratch or groove" (see rifle (v.1)). Related: Rifled; rifling.