Is it ensure, insure, or assure?
"divination by means of a cock and grains of corn," 1680s, from Latinized form of Greek alektryon "cock" + manteia "oracle" (see -mancy). The first element is literally "warder-off, fighter," related to alexein "to ward off, drive or keep off" (see Alexander). And cf. Alekto, one of the three Furies.