Etymograph

English

infidel

Infidel comes from Middle French infidèle ‘unfaithful’, from Latin fidēlis ‘faithful’, and ultimately from Proto-Indo-European *bʰeydʰ- ‘to command, to persuade, to trust’.

  1. Proto-Indo-Europeanc. 4500–2500 BCE*bʰeydʰ-1‘to command, to persuade, to trust’reconstructed
  2. Latinc. 75 BCE–200 CEfidēs2‘faith, trust’
  3. Latinc. 75 BCE–200 CEfidēlis3‘faithful’
  4. Latinc. 75 BCE–200 CEīnfidēlis3‘unfaithful’
  5. Middle Frenchc. 1400–1600infidèle3‘unfaithful’
  6. Englishearliest quotation 1779infidel3

attested reconstructed ? uncertain or disputed deepest recorded ancestor

  1. 1 Wiktionary, Latin fides
  2. 2 Wiktionary, Latin fidelis
  3. 3 Wiktionary, English infidel
  4. Earliest quotation in Wiktionary’s entry: 1779, Vicesimus Knox: “The infidel writer is a greater enemy to society.”.

Lineage

  1. Proto-Indo-Europeanc. 4500–2500 BCE*bʰeydʰ-Wiktionary, Latin fides‘to command, to persuade, to trust’reconstructed
  2. Latinc. 75 BCE–200 CEfidēsWiktionary, Latin fidelis‘faith, trust’
  3. Latinc. 75 BCE–200 CEfidēlisWiktionary, English infidel‘faithful’
  4. Latinc. 75 BCE–200 CEīnfidēlisWiktionary, English infidel‘unfaithful’
  5. Middle Frenchc. 1400–1600infidèleWiktionary, English infidel‘unfaithful’
  6. Englishearliest quotation 1779infidelWiktionary, English infidel. Earliest quotation in Wiktionary’s entry: 1779, Vicesimus Knox: “The infidel writer is a greater enemy to society.”

The story

First attested 1460, from Middle French infidèle, from Latin īnfidēlis (‘unfaithful’), from in- (‘not’) + fidēlis (‘faithful’).

Full etymology on Wiktionary

Linked words

through Proto-Indo-European *bʰeydʰ- ‘to command, to persuade, to trust’

federal, federation, confidence, confident, confederate, defy, defiance, abide, affidavit, bode, fiduciary, foi, confidant, bide, confide, diffident, 26 more

through Latin fidēs ‘faith, trust’

perfidy, 6 more

through Latin fidēlis ‘faithful’

fidelity, fealty, 2 more

Today it means

adj Rejecting a specific religion.

Sources

Sources: Wiktionary, “infidel”; the older steps come from the Wiktionary entries for Latin fides, Latin fidelis. By Wiktionary contributors, CC BY-SA 4.0, via kaikki.org (dump of Oct 3 2026); text adapted and restructured. Language periods are conventional ranges, not dates for this word. License.

Etymograph / Proto-Indo-European *bʰeydʰ- / infidel

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