defyyoudaoicibaDictYouDict[defy 词源字典]
defy: [14] The underlying notion of defy is of the renunciation of allegiance. It comes via Old French defier from a Vulgar Latin *disfidāre ‘renounce one’s faith’, a compound verb formed from the prefix dis-, denoting reversal, and Latin fīdus ‘trusting’. This adjective came from a lengthened variant of the stem which produced fidēs ‘faith’, source of English faith.

The word’s current main sense represents a slight shift from ‘being disloyal’ to actively ‘challenging someone’s power’. The verb’s noun derivative defiance [14], borrowed from Old French, has a first cousin in diffidence [15], originally ‘distrustfulness’, which came from the classical Latin compound verb diffidere ‘mistrust’.

=> diffidence, faith[defy etymology, defy origin, 英语词源]
back (n.)youdaoicibaDictYouDict
Old English bæc "back," from Proto-Germanic *bakam (cognates: Old Saxon and Middle Dutch bak, Old Frisian bek), with no known connections outside Germanic. In other modern Germanic languages the cognates mostly have been ousted in this sense ib words akin to Modern English ridge (cognates: Danish ryg, German Rücken). Many Indo-European languages show signs of once having distinguished the horizontal back of an animal (or a mountain range) from the upright back of a human. In other cases, a modern word for "back" may come from a word related to "spine" (Italian schiena, Russian spina) or "shoulder, shoulder blade" (Spanish espalda, Polish plecy).

To turn (one's) back on (someone or something) "ignore" is from early 14c. Behind (someone's) back "clandestinely" is from late 14c. To know (something) like the back of one's hand, implying familiarity, is first attested 1893. The first attested use of the phrase is from a dismissive speech made to a character in Robert Louis Stevenson's "Catriona":
If I durst speak to herself, you may be certain I would never dream of trusting it to you; because I know you like the back of my hand, and all your blustering talk is that much wind to me.
The story, a sequel to "Kidnapped," has a Scottish setting and context, and the back of my hand to you was noted in the late 19th century as a Scottish expression meaning "I will have nothing to do with you" [see Longmuir's edition of Jamieson's Scottish dictionary]. In English generally, the back of (one's) hand has been used to imply contempt and rejection since at least 1300. Perhaps the connection of a menacing dismissal is what made Stevenson choose that particular anatomical reference.
bide (v.)youdaoicibaDictYouDict
Old English bidan "to stay, continue, live, remain," also "to trust, rely," from Proto-Germanic *bidan "to await" (cognates: Old Norse biða, Old Saxon bidan, Old Frisian bidia, Middle Dutch biden, Old High German bitan, Gothic beidan "to wait"), which is of uncertain origin. Possibly from PIE *bheidh- "to trust" (via notion of "to await trustingly"). Preserved in Scotland and northern England, replaced elsewhere by abide in all senses except to bide one's time. Related: Bided; biding.
confidence (n.)youdaoicibaDictYouDict
early 15c., from Middle French confidence or directly from Latin confidentia, from confidentem (nominative confidens) "firmly trusting, bold," present participle of confidere "to have full trust or reliance," from com-, intensive prefix (see com-), + fidere "to trust" (see faith). For sense of "swindle" see con (adj.).
confident (adj.)youdaoicibaDictYouDict
1570s, "self-reliant, sure of oneself," from Middle French confident, from Latin confidentem (nominative confidens) "firmly trusting, reliant, self-confident, bold, daring," present participle of confidere (see confidence). Related: Confidently.
diffidence (n.)youdaoicibaDictYouDict
c. 1400, from Latin diffidentia "mistrust, distrust, want of confidence," from diffidere "to mistrust, lack confidence," from dis- "away" (see dis-) + fidere "to trust" (see faith). Modern sense is of "distrusting oneself" (1650s). The original sense was the opposite of confidence.
distrustyoudaoicibaDictYouDict
early 15c. (v.); 1510s (n.), from dis- + trust. "The etymologically correct form is mistrust, in which both elements are Teutonic" [Klein]. Related: Distrusted; distrusting; distrustful; distrustfully; distrustfulness.
entrust (v.)youdaoicibaDictYouDict
also intrust, c. 1600, from en- (1) "make, put in" + trust (n.). Related: Entrusted; entrusting.
leery (adj.)youdaoicibaDictYouDict
"untrusting, suspicious, alert," 1718, originally slang, with -y (2), and perhaps from dialectal lere "learning, knowledge" (see lore), or from leer (v.) in some now-obscure sense. OED suggests connection with archaic leer (adj.) "empty, useless," a general Germanic word (cognate with German leer, Dutch laar), of unknown origin.
mistrust (v.)youdaoicibaDictYouDict
late 14c., from mis- (1) + trust (v.). Related: Mistrusted; mistrusting.
perfidy (n.)youdaoicibaDictYouDict
1590s, from Middle French perfidie (16c.), from Latin perfidia "faithlessness, falsehood, treachery," from perfidus "faithless," from phrase per fidem decipere "to deceive through trustingness," from per "through" (see per) + fidem (nominative fides) "faith" (see faith).
[C]ombinations of wickedness would overwhelm the world by the advantage which licentious principles afford, did not those who have long practiced perfidy grow faithless to each other. [Samuel Johnson, "Life of Waller"]
trust (v.)youdaoicibaDictYouDict
c. 1200, from Old Norse treysta "to trust, rely on, make strong and safe," from traust (see trust (n.)). Related: Trusted; trusting.
trustful (adj.)youdaoicibaDictYouDict
1570s, "trustworthy," from trust (n.) + -ful. Meaning "trusting" attested from 1832. Related: Trustfully, trustfulness.
trusty (adj.)youdaoicibaDictYouDict
early 13c., "trusting," from trust (n.) + -y (2). Old English expressed this idea by treowful. Meaning "reliable, to be counted on" is from early 14c. The noun meaning "trustworthy person" is from 1570s; specifically as "a prisoner granted special privileges as reward for good conduct" by 1855.
tryst (n.)youdaoicibaDictYouDict
late 14c., "appointment to meet at a certain time and place," from Old French tristre "waiting place, appointed station in hunting," probably from a Scandinavian source such as Old Norse treysta "to trust, make firm" (see trust (v.)). The notion would be "place one waits trustingly." As a verb, late 14c. Related: Trysting.