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infidelis

Etymology and origin of the Latin word infidelis

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Confidence
Established
Formation
Derivation
First attested
Plautus
Ultimate origin
Latin (fidēs)

Pronunciation

  • IPA (Classical): [ĩː.fɪˈdeː.lɪs][1]
  • IPA (Ecclesiastical): [iɱ.fiˈdɛː.lis][1]

Forms

īnfidēlis (neuter īnfidēle, comparative īnfidēlior, adverb īnfidēliter); third-declension two-termination adjective[1]

Etymology

It is from in- “not” and fidēlis “faithful”.[2][1][3]

Earliest recorded meaning

Köbler's first source is Plautus, whom he dates c. 250–184 BC.[4]

Semantic evolution

It meant not keeping faith, treacherous, disloyal.[2] Döderlein explains that fīdus is trustworthy by nature, fidēlis faithful as a moral quality.[5]

In Late Latin it came to mean unbelieving, and Ecclesiastical Latin uses it for unfaithful, unbelieving.[3][6] Medieval Latin used it for disloyal, guilty of treason, and untrustworthy.[7] British Medieval Latin used it of the disloyal, as Alcuin, who says he was never unfaithful to King Offa.[8] Through French infidèle it gave English infidel in the mid-15th century, an adherent of a religion opposed to Christianity.[1][3]

Timeline

  • c. 250–184 BC – Plautus uses it.[4]
  • c. 796 – Alcuin uses it of disloyalty.[8]
  • mid-15th century – English infidel is recorded.[3]

Meanings

Adjective

  1. Faithless, treacherous, disloyal.[2]
  2. (Ecclesiastical Latin) Unbelieving; as a noun, an infidel.[6][3]

Word family

  • īnfidēlitās

Usage notes

Döderlein distinguishes fīdus from fidēlis.[5]

References

  1. ^ a b c d e Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c Glare, P. G. W., ed. (2012), Oxford Latin Dictionary, 2nd ed., Oxford: Oxford University Press
  3. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  4. ^ a b Köbler, Gerhard (2010), Lateinisches Abkunfts- und Wirkungswörterbuch für Altertum und Mittelalter, online ed., koeblergerhard.de
  5. ^ a b Döderlein, Ludwig (1874), Döderlein’s Hand-book of Latin Synonymes, tr. H. H. Arnold, Andover: W. F. Draper
  6. ^ a b Stelten, Leo F. (1995), Dictionary of Ecclesiastical Latin, Peabody, Mass.: Hendrickson
  7. ^ Niermeyer, J. F. (1976), Mediae Latinitatis Lexicon Minus, Leiden: Brill
  8. ^ a b Latham, R. E., D. R. Howlett, R. K. Ashdowne, et al. (1975–2013), Dictionary of Medieval Latin from British Sources, London: British Academy / Oxford University Press
Cite this entry

“Infidelis.” Etymologically, 16 Oct. 2026, etymologically.com/la/infidelis. Accessed 16 Oct. 2026.

Last edited on . ·