1696, variant of M.E.
key "wharf" (1306), from O.N.Fr.
cai (O.Fr.
chai) "sand bank," from Gaulish
caium (5c.), from O.Celt.
*kagio- "to encompass, enclose" (cf. Welsh
cae "fence, hedge," Cornish
ke "hedge"), cognate with O.E.
haga "hedge" (see
hedge). Spelling altered by infl. of Fr.
quai, from the same Celtic source.