recreant (adj.)

c. 1300, "confessing oneself to be overcome or vanquished," from Old French recreant "defeated, vanquished, yielding, giving; weak, exhausted; cowardly," present-participle adjective from recroire "to yield in a trial by combat, surrender allegiance," literally "believe again;" perhaps on notion of "take back one's pledge, yield one's cause," from re- "again, back" (see re-) + croire "entrust, believe," from Latin credere (see credo).

Non sufficit ... nisi dicat illud verbum odiosum, quod recreantus sit. [Bracton, c. 1260]

Meaning "cowardly" in English is from late 14c. Meaning "unfaithful to duty" is from 1640s.

"one who yields in combat, one who begs for mercy, one who admits defeat," early 15c., hence "coward, faint-hearted wretch;" from recreant (adj.) and from Old French recreant as a noun, "one who acknowledges defeat, a craven, coward, renegade, traitor, wretch." In English, sense of "apostate, deserter, villain" is from 1560s.