Falcon
Middle English faucon (originally denoting any diurnal bird of prey used in falconry): from Old French, from late Latin falco, from Latin falx, falc- ‘sickle’, or of Germanic origin and related to Dutch valk and German Falke . The -l- was added in the 15th century to conform with the Latin spelling.
wiktionary
From Middle English faucoun, falcon, faulcon, from Old French falcun, from Late Latin falcō(“falcon”), of Germanic origin, probably via Frankish *falkō(“falcon, hawk”), from Proto-Germanic *falkô(“falcon”), from Proto-Indo-European *pol̑-(“pale”), from *pel-(“fallow”).
etymonline
falcon (n.)
mid-13c., faucon, from Old French faucon "falcon" (12c.), from Late Latin falconem (nominative falco) "falcon" (source also of Old Spanish falcon, Portuguese falcão, Italian falcone, Old High German falcho, German Falke, Dutch valk), probably from Latin falx (genitive falcis) "curved blade, pruning hook, sickle, war-scythe" (see falcate); the bird said to be so called for the shape of its talons, legs, or beak, but also possibly from the shape of its spread wings.
The other theory is that the Latin bird name falx is of Germanic origin and means "gray bird" (from PIE root *pel- (1) "pale"), which is supported by the antiquity of the word in Germanic but opposed by those who point out that falconry by all evidences was imported from the East, and the Germans got it from the Romans, not the other way round.
