Etymology
Advertisement
confide (v.)

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.

Related entries & more 
Advertisement
*bheidh- 
Proto-Indo-European root meaning "to trust, confide, persuade."

It forms all or part of: abide; abode; affiance; affidavit; auto-da-fe; bide; bona fide; confederate; confidant; confide; confidence; confident; defiance; defy; diffidence; diffident; faith; fealty; federal; federate; federation; fiancee; fideism; fidelity; fiducial; fiduciary; infidel; infidelity; nullifidian; perfidy; solifidian.

It is the hypothetical source of/evidence for its existence is provided by: Greek pistis "faith, confidence, honesty;" Latin fides "trust, faith, confidence, reliance, credence, belief;" Albanian be "oath," bindem "to be convinced, believe;" Old Church Slavonic beda "distress, necessity," bediti "to force, persuade;" Old English biddan "to ask, beg, pray," German bitten "to ask."
Related entries & more 
confident (adj.)

1570s, "self-reliant, sure of oneself;" c. 1600, "fully assured, having strong belief," from French confident, from Latin confidentem (nominative confidens) "firmly trusting, reliant, self-confident, bold, daring," present participle of confidere "to have full trust or reliance," from assimilated form of com, here perhaps an intensive prefix (see com-), + fidere "to trust" (from PIE root *bheidh- "to trust, confide, persuade"). Related: Confidently.

Related entries & more 
confidence (n.)
Origin and meaning of confidence

c. 1400, "assurance or belief in the good will, veracity, etc. of another," from Old 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 assimilated form of com, here perhaps an intensive prefix (see com-), + fidere "to trust" (from PIE root *bheidh- "to trust, confide, persuade").

From mid-15c. as "reliance on one's own powers, resources, or circumstances, self-assurance." Meaning "certainty of a proposition or assertion, sureness with regard to a fact" is from 1550s. Meaning "a secret, a private communication" is from 1590s. The connection with swindling (see con (adj.)) dates to mid-19c. and comes from the notion of the false "trustworthiness" which is the key to the game.

Related entries & more 
fideism (n.)
in various theological doctrines making knowledge dependent on faith, 1885, from Latin fides "faith" (from PIE root *bheidh- "to trust, confide, persuade") + -ism.
Related entries & more 
Advertisement
confidant (n.)

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.

Related entries & more 
fiducial (adj.)
1570s, "assumed as a fixed basis for comparison," from Latin fiducialis "reliable," from fiducia "trust" (from PIE root *bheidh- "to trust, confide, persuade"). From 1620s as "pertaining to trust;" 1832 as "fiduciary."
Related entries & more 
fealty (n.)
c. 1300, feaute, from Old French feauté, earlier fealte, "loyalty, fidelity; homage sworn by a vassal to his overlord; faithfulness," from Latin fidelitatem (nominative fidelitas) "faithfulness, fidelity," from fidelis "loyal, faithful" (from PIE root *bheidh- "to trust, confide, persuade").
Related entries & more 
nullifidian (n.)

"one of no faith or religion," 1560s, from Latin nulli-, combining form of nullus "no" (see null) + fides "faith" (from PIE root *bheidh- "to trust, confide, persuade"). As an adjective from 1620s.

Related entries & more 
federation (n.)

1721, "union by agreement," from French fédération, from Late Latin foederationem (nominative foederatio), noun of action from past-participle stem of Latin foederare "league together," from foedus "covenant, league" (from PIE root *bheidh- "to trust, confide, persuade").

Related entries & more