Etymologically

Etymology and origin of the Latin word infirmo

Confidence
Established
Formation
Derivation
First attested
170–c. 90 BC, Accius
Ultimate origin
Proto-Indo-European (*dʰer-mo-)
Etymology tree
inherited borrowed derived
Latin firmus
French ferme
Latin infirmus
Latin infirmitas
Latin infirmo
Latin firmitas
Latin firmo
English firm
French fermer
French enfermer
French refermer

Pronunciation

  • Classical: [ĩːˈfɪr.moː][1]
  • Ecclesiastical: [iɱˈfir.mo][1]

Forms

īnfirmō (present infinitive īnfirmāre, perfect active īnfirmāvī, supine īnfirmātum); first conjugation[1]

Etymology

It is from Latin īnfirmus (“weak”) + -ō.[2][3][1] De Vaan, who dates the verb from Accius, traces firmus (“firm, strong”) to Proto-Italic *fermo- and Proto-Indo-European *dʰer-mo- (“holding”), comparing Sanskrit धर्मन् (dhárman-, “support, firm hold, law”).[4]

Earliest recorded meaning

Accius has it first: “no lowliness ever weakens a good nature”.[2][4][5]

Semantic evolution

It is to weaken physically, as Sallust has new walls weakened by damp, and to deprive of military strength, as Cicero fears delays that weaken Brutus and strengthen Antony.[2][6] It is also to unnerve.[2] In argument and law it is to lessen the force of something: to refute or deny a contention, as in the Rhetorica ad Herennium, and to annul or invalidate acts and laws, as Cicero accuses an opponent of trying to undo a grant made by Pompey.[2][6][1] Paul the Deacon's Festus explains abrogāre by it.[3] Church Latin glosses it to weaken, annul or refute.[7]

Timeline

  • 170–c. 90 BC – Accius of weakening a good nature.[2][5]
  • 86/82 BC – The Rhetorica ad Herennium of refuting an argument.[2][5]
  • 81–43 BC – Cicero of invalidating a grant.[2][5]
  • 86–34 BC – Sallust of walls weakened by damp.[2][5]

Meanings

Verb

  1. To weaken, enfeeble; to deprive of military strength.[2][6][7][1]
  2. To unnerve, dishearten.[2]
  3. To lessen the authority of; to refute, disprove.[2][6][7][1]
  4. To annul, invalidate.[2][7]

Word family

  • īnfirmātiō

Usage notes

The TLL lists a separate and doubtful īnfirmō, from in and firmāre, meaning to strengthen or confirm, known only from one passage of Caelius Aurelianus.[3][6]

References

  1. ^ a b c d e f g Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g h i j k l m Glare, P. G. W., ed. (2012), Oxford Latin Dictionary, 2nd ed., Oxford: Oxford University Press
  3. ^ a b c Thesaurus linguae Latinae (1900–), Leipzig: Teubner; Berlin: De Gruyter; open-access ed., Munich: Bayerische Akademie der Wissenschaften
  4. ^ a b de Vaan, Michiel (2008), Etymological Dictionary of Latin and the other Italic Languages, Leiden Indo-European Etymological Dictionary Series 7, Leiden; Boston: Brill
  5. ^ a b c d e Köbler, Gerhard (2010), Lateinisches Abkunfts- und Wirkungswörterbuch für Altertum und Mittelalter, online ed., koeblergerhard.de
  6. ^ a b c d e Lewis, Charlton T.; Short, Charles (1879), A Latin Dictionary, Oxford: Clarendon Press
  7. ^ a b c d Stelten, Leo F. (1995), Dictionary of Ecclesiastical Latin, Peabody, Mass.: Hendrickson
Cite this entry

“Infirmo.” Etymologically, 19 Oct. 2026, etymologically.com/la/infirmo. Accessed 20 Oct. 2026.

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