Word Origin & Historyfalse c.1200, from O.Fr. fals, faus, from L. falsus "deceived, erroneous, mistaken," pp. of fallere "deceive, disappoint," of uncertain origin. Adopted into other Gmc. languages (cf. Ger. falsch, Dan. falsk), though English is the only one in which the active sense of "deceitful" (a secondary sense in L.) has predominated. Related: Falsely. Falsies "padded bras