c. 1300, "enfeebled; wearied, exhausted," from Old French faint, feint "false, deceitful; sham, artificial; weak, faint, lazy, indolent, cowardly," past participle of feindre "hesitate, falter, be indolent, show weakness, avoid one's duty by pretending," from Latin fingere "to touch, handle; devise; fabricate, alter, change" (from PIE root *dheigh- "to form, build"). Also from c. 1300 as "deceitful; unreliable; false." Meaning "wanting in spirit or courage, cowardly" (a sense now mostly encountered in faint-hearted) is from early 14c. From early 15c. of actions, functions, colors, etc., "weak, feeble, poor." Meaning "producing a feeble impression upon the senses" is from 1650s.
c. 1300, "grow weak, become enfeebled," also "lack courage or spirit, be faint-hearted," and "to pretend, feign;" from faint (adj.). Sense of "swoon, lose consciousness" is from c. 1400. Also used in Middle English of the fading of colors, flowers, etc. Related: Fainted; fainting. For Chaucer and Shakespeare, also a transitive verb ("It faints me").
c. 1300, "faintness, faint-heartedness," from faint (adj.). From 1808 as "a swoon."