Is it ensure, insure, or assure?
"perplex, embarrass," early 15c., earlier "lose one's composure, be upset" (late 14c.), from Old French esbaiss-, present stem of esbaer "gape with astonishment," from es "out" (see ex-) + ba(y)er "to be open, gape," from Latin *batare "to yawn, gape," from root *bat, possibly imitative of yawning. Related: Abashed; abashing. Bashful is a 16c. derivative.