Middle English abiden, from Old English abidan, gebidan "remain, wait, wait for, delay, remain behind," from ge- completive prefix (denoting onward motion; see a- (1)) + bidan "bide, remain, wait, dwell" (see bide).

Originally intransitive (with genitive of the object: we abidon his "we waited for him"); the transitive senses of "endure, sustain, stay firm under," also "tolerate, bear, put up with" (now usually with a negative) are from c. 1200. To abide with "stay with (someone); live with; remain in the service of" is from c. 1300. 

Related: Abided; abiding. The historical conjugation was abide, abode, abidden, but in Modern English the formation generally is weak.

mid-13c., "action of waiting," verbal noun from abiden "to abide" (see abide). It is formally identical with the old, strong past participle of abide (Old English abad), but the modern conjugation is weak and abided is used. The present-to-preterite vowel change is consistent with an Old English class I strong verb (ride/rode, etc.). The meaning "habitual residence" is attested by 1570s.

1520s, "to promise," from Old French afiancier "to pledge, promise, give one's word," from afiance (n.) "confidence, trust," from afier "to trust," from Late Latin affidare, from ad "to" (see ad-) + fidare "to trust," from fidus "faithful" (from PIE root *bheidh- "to trust, confide, persuade").

From mid-16c. especially "to promise in marriage." The earlier form of the word was affy (Middle English affien "to trust, have faith; have faith in" c. 1300), from Old French afier. Related: Affianced; affiancing.

"written declaration upon an oath," 1590s, from Medieval Latin affidavit, literally "he has stated on oath," third person singular perfective of affidare "to trust; to make an oath," from Latin ad "to" (see ad-) + fidare "to trust," from fidus "faithful" (from PIE root *bheidh- "to trust, confide, persuade"). So called from being the first word of sworn statements.

"sentence passed by the Inquisition" (plural autos-da-fé), 1723, from Portuguese auto-da-fé "judicial sentence, act of the faith," especially the public burning of a heretic, from Latin actus de fide. The elements are auto "a play," in law, "an order, decree, sentence," from Latin actus (see act (v.)), de "from, of" (see de), fides "faith" (from PIE root *bheidh- "to trust, confide, persuade"). The Spanish form is auto-de-fe, but the Portuguese form took hold in English, perhaps through popular accounts of the executions following the earthquake of 1755.

Middle English biden, from Old English bidan "to stay, continue, live, remain," also "to trust, rely," from Proto-Germanic *bidan "to await" (source also of 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. According to Watkins possibly from PIE root *bheidh- "to trust, confide, persuade" (via notion of "to await trustingly").

Frequent in Middle English (to bide on live was "stay alive;" bide in bay was "stand at bay"). It was preserved in Scotland and northern England, displaced elsewhere by abide in all senses except in the expression bide (one's) time.  "I Bide My Time" is said to be "the motto of the earls of Loudon" in a Scottish context [1806, in a note to "Poetical Words of Sir David Lyndsay"], and it may owe its popularity to Scott's significant use of it in "The Bride of Lammermoor":

Ravenswood, who had assumed the disguise of a sewer upon the occasion, answered, in a stern voice, "I bide my time;" and at the same moment a bull's head, the ancient symbol of death, was placed upon the table. The explosion of the conspiracy took place upon the signal, and the usurper and his followers were put to death.

Related: Bided; biding.

1540s, "genuinely, with sincerity," Latin, literally "in or with good faith," ablative of bona fides "good faith" (see faith). Originally in English an adverb, later (18c.) also an adjective, "acting or done in good faith." The opposite is mala fide.

1530s, "to unite in a league or alliance," from Late Latin confoederatus, past participle of confoederare "to unite by a league," from assimilated form of com "with, together" (see con-) + foederare, from foedus (genitive foederis) "a league," from suffixed form of PIE root *bheidh- "to trust, confide, persuade."

The older verb was confeder (late 14c.), from Old French confederer, Medieval Latin confederare. Related: Confederated; confederating.

1610s, confident, "(male) person trusted with private affairs," from French confident (16c.), from Italian confidente "a trusty friend," literally "confident, trusty," from Latin confidentem (nominative confidens), present participle of confidere "to trust, confide," from assimilated form of com, here perhaps an intensive prefix (see com-), + fidere "to trust" (from PIE root *bheidh- "to trust, confide, persuade"). The spelling with -a- and the pronunciation with the stress on the last syllable came to predominate 18c. and might reflect the French pronunciation.

mid-15c., "to place trust or have faith," from Latin confidere "to trust in, rely firmly upon, believe," from assimilated form of com, here perhaps an intensive prefix (see com-), + fidere "to trust" (from PIE root *bheidh- "to trust, confide, persuade"). Meaning "to share a secret with, take into one's confidence" is from 1735; phrase confide in (someone) is from 1888. Related: Confided; confiding.