Fidelity
late Middle English: from Old French fidelite or Latin fidelitas, from fidelis ‘faithful’, from fides ‘faith’. Compare with fealty.
wiktionary
15th century, from Middle English[Term?], from Middle French fidélité, from Latin fidēlitās, from fidēlis(“faithful”), from fidēs(“faith, loyalty”) (English faith), from Proto-Indo-European *bʰidʰ-, zero-grade of *bʰeydʰ-(“to command, to persuade, to trust”) (English bide). Doublet of fealty.
etymonline
fidelity (n.)
early 15c., "faithfulness, devotion," from Old French fidélité (15c.), from Latin fidelitatem (nominative fidelitas) "faithfulness, adherence, trustiness," from fidelis "faithful, true, trusty, sincere," from fides "faith" (from PIE root *bheidh- "to trust, confide, persuade"). From 1530s as "faithful adherence to truth or reality;" specifically of sound reproduction from 1878.
