"to reduce, to lessen in intensity," c.1300, shortening of abate (q.v.). Now only in phrase bated breath, which was used by Shakespeare in "The Merchant of Venice" (1596).
c.1300, "to contend with blows or arguments," from Old French batre "to hit, beat, strike," from Late Latin battere, from Latin batuere "to beat, knock" (see batter (v.)). In falconry, "to beat the wings impatiently and flutter away from the perch." Figurative sense of "to flutter downward" attested from 1580s.