LATIN DICTIONARYLexicon Latīnum
suffixfirst/second-declension suffix

-acus1

-acus (feminine -aca, neuter -acum)

Meaning

  1. morphemesuffixSuffixed to nouns to create adjectives
    Corinthus + -acus → Corinthiacus

Origins

  1. Ancient Greek -κός(-kós)
  2. Latin-acus

Ancient Greek -ακός (-akós)der. Latin -acus From Ancient Greek -ακός (-akós, adjective-forming suffix).

Descendants
  • English-ac
suffixfirst/second-declension suffix
-ācus2
-ācus (feminine -āca, neuter -ācum)

Meaning

  1. morphemesuffixSuffixed to nouns to create adjectives, often substantivised in toponyms.
    Aurēlius + -ācus → Aurēliācum
    Paulus + -ācus → Pauliācus

Origins

Proto-Celtic *-ākosder. Gaulishder. Latin -acus From Gaulish, from Proto-Celtic *-ākos (adjective-forming suffix).

Quick answers

What does -acus mean in Latin?
-acus, a suffix, means “Suffixed to nouns to create adjectives”.
Where does -acus come from?
Ancient Greek -κός (-kós) → Latin -acus.