"young deer," mid-14c., from Anglo-French (late 13c.), Old French faon, feon "young animal" (12c.), from Vulgar Latin *fetonem (nominative *feto), from Latin fetus "an offspring" (see fetus). Still used of the young of any animal in King James I's private translation of the Psalms, but mainly of deer from 15c. Color use is 1881.
Old English fægnian "rejoice, be glad, exult," from fægen "glad" (see fain); used in Middle English to refer to expressions of delight, especially a dog wagging its tail (early 13c.), hence "court favor, grovel, act slavishly" (early 14c.). Related: Fawned; fawning.