mid-15c., falsifien, "to prove false," from Old French falsifier "to falsify, counterfeit" (15c.), from Late Latin falsificare "make false, corrupt," from Latin falsus "erroneous, mistaken" (see false). Meaning "to make false" is from c. 1500. Earlier verb was simply falsen (c. 1200). Related: Falsified; falsifying.
"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).
1610s, "to alter or enlarge (a writing) by inserting new material," from Latin interpolatus, past participle of interpolare "alter, freshen up, polish;" of writing, "falsify," from inter "among, between" (see inter-) + polare, which is related to polire "to smoothe, polish," from PIE root *pel- (5) "to thrust, strike, drive," the connecting notion being "to full cloth" [Watkins].
Sense evolved in Latin from "refurbish," to "alter appearance of," to "falsify (especially by adding new material)." Middle English had interpolen (early 15c.) in a similar sense. Related: Interpolated; interpolating.
1650s, from Late Latin interpolator "one who corrupts or spoils," agent noun from past participle stem of Latin interpolare "to polish; to alter; to falsify" (see interpolate).
1610s, "act of interpolating;" 1670s, "that which is interpolated," from French interpolation (17c.) or directly from Latin interpolationem (nominative interpolatio), noun of action from past participle stem of interpolare "to alter; falsify" (see interpolate).
1590s, "to confer the degree of doctor on," from doctor (n.). Meaning "to treat as a doctor, administer medical treatment to" is from 1712; sense of "alter, disguise for the purpose of deception, falsify" is from 1774. Related: Doctored; doctoring.
c. 1500, "act of adulterating; state of being debased by mixture with something else," generally of inferior quality, from Latin adulterationem (nominative adulteratio) "an adulteration, sophistication," noun of action from past-participle stem of adulterare "corrupt, falsify; debauch; commit adultery," from ad "to" (see ad-) + alterare "to alter" (see alter), though Watkins explains it as ad alterum "(approaching) another (unlawfully)." Meaning "a result of adulterating" is from 1650s.
"debase by mixing with foreign or inferior material, make corrupt," 1530s, back-formation from adulteration, or else from Latin adulteratus, past participle of adulterare "to falsify, corrupt," also "to commit adultery." An earlier verb was adulter (late 14c. in the sense "make impure"), directly from the Latin verb, but this English verb also carried the meaning "commit adultery." Related: Adulterated; adulterating.
early 14c., "to counterfeit" (a letter, document, etc.), from Old French forgier "to forge, work (metal); shape, fashion; build, construct; falsify" (12c., Modern French forger), from Latin fabricari "to frame, construct, build," from fabrica "workshop" (see forge (n.)). Meaning "to counterfeit" (a letter, document, or other writing) is from early 14c.; literal meaning "to form (something) by heating in a forge and hammering" is from late 14c. in English, also used in Middle English of the minting of coins, so that it once meant "issue good money" but came to mean "issue spurious (paper) money." Related: Forged; forging.