köken: Inherited from Middle French faulx, from Old French fauz, faus, fals, from Latin falsus.
aile: aile fausse, alpiste faux-roseau, archi-faux, archifaux, baldingère faux-roseau, démêler le vrai du faux, être faux comme un jeton, faire fausse queue, faire fausse route, faire faux bond
köken: Inherited from Old Spanish falso, from Latin falsus, with preservation of /alC/ and initial /f/, which Coromines & Pascual suppose is the result of learned pronunciation habits.