falsify v.

late Old English, "intentionally untrue, lying," of religion, "not of the true faith, not in accord with Christian doctrines," from Old French fals, faus "false, fake; incorrect, mistaken; treacherous, deceitful" (12c., Modern French faux), from Latin falsus "deceptive, feigned, deceitful, pretend," also "deceived, erroneous, mistaken," past participle of fallere "deceive, disappoint," which is of uncertain origin (see fail (v.)).

Adopted into other Germanic languages (cognates: German falsch, Dutch valsch, Old Frisian falsk, Danish falsk), though English is the only one in which the active sense of "deceitful" (a secondary sense in Latin) has predominated. From c. 1200 as "deceitful, disloyal, treacherous; not genuine;" from early 14c. as "contrary to fact or reason, erroneous, wrong." False alarm recorded from 1570s. False step (1700) translates French faux pas. To bear false witness is attested from mid-13c. False prophet "one who prophecies without divine commission or by evil spirits," is attested from late 13c.

1610s, from falsify + -able or from French falsifiable. Related: Falsifiability.

"act of making false, false representation; a showing to be false or erroneous," 1560s, from Late Latin falsificationem (nominative falsificatio), noun of action from past-participle stem of falsificare "to falsify" (see falsify).