A 17c. respelling of fain, fein, from Middle English feinen, feynen "disguise or conceal (deceit, falsehood, one's real meaning); dissemble, make false pretenses, lie; pretend to be" (c. 1300), from Old French feindre "hesitate, falter; be indolent; lack courage; show weakness," also transitive, "to shape, fashion; depict, represent; feign, pretend; imitate" (12c.), from Latin fingere "to touch, handle; devise; fabricate, alter, change" (from PIE root *dheigh- "to form, build").
From late 14c. as "simulate (an action, an emotion, etc.)." Related: Feigned; feigning. The older spelling is that of faint, feint, but this word acquired a -g- in imitation of the French present participle stem feign- and the Latin verb.