faultyoudaoicibaDictYouDict[fault 词源字典]
fault: [13] Like fail, fallacy, fallible, and false, fault comes ultimately from Latin fallere ‘deceive, fail’. Its past participle formed the basis of a Vulgar Latin noun *fallita ‘failing, falling short’, which passed into English via Old French faute in the sense ‘lack, deficiency’. The notion of ‘moral culpability’ does not seem to have become incorporated into the word until the late 14th century.
=> fail, fallacy, fallible, false[fault etymology, fault origin, 英语词源]
fault (n.)youdaoicibaDictYouDict
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.
fault (v.)youdaoicibaDictYouDict
"find fault with," mid-15c. from fault (n.). Earlier it was used in an intransitive sense of "be deficient" (late 14c., Scottish). Related: Faulted; faulter; faulting.