Is it ensure, insure, or assure?
late 14c., "to pull or gather up," earlier "to pluck, stretch" (late 13c., implied in tucker), probably from Middle Low German or Middle Dutch tucken "pull up, draw up, tug" (cognate with Old English tucian "mistreat, torment," and related to Old English togian "to pull," German zucken; see tow). Sense of "thrust into a snug place" is first recorded 1580s. Slang meaning "to consume, swallow" is recorded from 1784. The noun is first attested late 14c.