1275-1325;Middle Englishabaishen < dialectal Old Frenchabacher,Old Frenchabaissier to put down, bring low (see abase), perhaps conflated with Anglo-Frenchabaiss-, long stem of abair,Old Frenchesba(h)ir to gape, marvel, amaze (es-ex-1 + -ba(h)ir, alteration of baer to open wide, gape < Vulgar Latin*batāre; cf. bay2, bay3)
c.1300, from O.Fr. esbaiss-, stem of esbaer "gape with astonishment," from es "out" + ba(y)er "to be open, gape," from L. *batare "to yawn, gape," from root *bat, possibly imitative of yawning. Bashful is a 16c. derivative.