fidelity n.

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."

"faithful," 1560s, not found in Middle English but apparently from Old French feal "faithful, loyal, true, sincere," collateral form of feeil, from Latin fidelis "loyal" (see fidelity).

1947, abbreviation of high-fidelity (1934), a descriptive term of radio receivers in reference to their quality of sound reproduction. Hi as an advertiser's phonological shortening of high (adj.) is attested by 1914. Fidelity in the sense "faithful reproduction of sound" is from 1878.