c. 1300, recreaunt, "confessing oneself to be overcome or vanquished, admitting defeat, surrendering, ready to yield in a fight," also a word of surrender, from Old French recreant "defeated, vanquished, yielding, giving; weak, exhausted; cowardly" (also used as a noun), 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, "De Legibus et Consuetudinibus Angliæ," c. 1260]
The extended meaning "cowardly" in English is from late 14c. The meaning "unfaithful to duty" is from 1640s. Middle English also had a verb recreien "to be cowardly, yield in battle" (mid-14c.).
"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, the sense of "apostate, deserter, villain" is from 1560s.