Is it ensure, insure, or assure?
Old English gelpan (Anglian), gielpan (West Saxon) "to boast," from Proto-Germanic *gelpanan (cf. Old Saxon galpon, Old Norse gjalpa "to yelp," Old Norse gjalp "boasting," Old High German gelph "outcry"), from PIE root *ghel- "to cry out" (see yell). Related: Yelped; yelping.
Old English gielp "boasting," from source of yelp (v.). Meaning "quick, sharp bark or cry" is attested from c.1500.