mid-15c., disappointen, "dispossess of appointed office," from dis- "reverse, opposite of" + appoint, or else from Old French desapointer "undo the appointment, remove from office" (14c., Modern French from désappointer). Modern sense of "to frustrate the expectations or desires of" is from late 15c. of persons; of plans, etc., "defeat the realization or fulfillment of," from 1570s, perhaps via a secondary meaning of "fail to keep an appointment."

"that frustrates hopes, falling short of expectations," 1520s, present-participle adjective from disappoint (v.). Related: Disappointingly.

"having one's anticipations or desires frustrated; baffled, balked, thwarted," 1550s, past-participle adjective from disappoint (v.). Related: Disappointedly; disappointedness.

1610s, "defeat or failure of hope or expectation," from French désappointement or else a native formation from disappoint + -ment. Meaning "feeling of being disappointed" is from 1756. Meaning "a thing that disappoints" is from 1756.

"act of frustrating, disappointment, defeat," 1550s, from Latin frustrationem (nominative frustratio) "a deception, a disappointment," noun of action from past-participle stem of frustrari "to deceive, disappoint, make vain," from frustra (adv.) "in vain, in error," which is related to fraus "injury, harm," a word of uncertain origin (see fraud). Earlier (mid-15c.) with a now-obsolete sense of "nullification."

"disappoint, offend, throw into a state of sulky dissatisfaction," 1680s, from dis-, here probably meaning "entirely, very," + obsolete gruntle "to grumble, utter a low grunt" (Middle English gruntelen, early 15c.), frequentative of grunt (v.); hence "to complain" (by 1560s). All citations in OED are in the form of the past-participle adjective.

"make of no avail, bring to nothing, prevent from taking effect or coming to fulfillment," mid-15c., from Latin frustratus, past participle of frustrari "to deceive, disappoint, make vain," from frustra (adv.) "in vain, in error," which is related to fraus "injury, harm," a word of uncertain origin (see fraud). Related: Frustrated; frustrating.

c. 1200, transitive, "to make worried or depressed; to make angry, enrage;" also "to be physically painful, cause discomfort;" c. 1300 as "cause grief to, disappoint, be a cause of sorrow;" also "injure, harass, oppress," from tonic stem of Old French grever "afflict, burden, oppress," from Latin gravare "make heavy; cause grief," from gravis "weighty" (from PIE root *gwere- (1) "heavy"). Intransitive sense of "be sorry, lament" is from c. 1400. Related: Grieved; grieving.

late 13c., faute, "deficiency," from Old French faute, earlier falte, "opening, gap; failure, flaw, blemish; lack, deficiency" (12c.), from Vulgar Latin *fallita "a shortcoming, falling," from Latin falsus "deceptive, feigned, spurious," past participle of fallere "deceive, disappoint" (see fail (v.)).

The -l- was restored 16c., probably in imitation of Latin, but the letter was silent until 18c. Sense of "physical defect" is from early 14c.; that of "moral culpability" (milder than sin or vice, but more serious than an error) is first recorded late 14c. Geological sense is from 1796. The use in tennis (c. 1600) is closer to the etymological sense.

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.