-arius

• (Classical Latin) IPA^(key): [aː.ri.ʊs]
• (modern Italianate Ecclesiastical) IPA^(key): [a.ri.us]

From earlier Proto-Italic *-ās-(i)jo- (cf. Oscan sakrasias and Umbrian plenasier), formed from *-āso- (from PIE *-eh₂so-, cf. the Hittite appurtenance suffix -ašša-^[1]), extended with the relational adjectival suffix *-yós (“belonging to”).

-ārius (feminine -āria, neuter -ārium); first/second-declension suffix

2. Used to form adjectives from nouns or numerals.

   ‎camera (“vault, arch”) + ‎-ārius → ‎camerārius (“climbing, creeping”)

   ‎ordō (“line, row”) + ‎-ārius → ‎ordinārius (“ordinary, of the rank and file”)

   ‎quaternī (“four at a time, by fours”) + ‎-ārius → ‎quaternārius (“quaternary”)

The nominative neuter form -arium, when appended to nouns, forms derivative nouns denoting a “place where things are kept”.

First/second-declension adjective.

• → French: -aire m or f by sense
• → Italian: -ario m

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.)

-ārius m (genitive -āriī or -ārī); second declension

2. (masculine only) -er; Used to form nouns denoting an agent of use, such as a dealer or artisan, from other nouns.

   ‎argentum (“silver”) + ‎-ārius → ‎argentārius (“banker”)

   ‎avicula (“little bird”) + ‎-ārius → ‎aviculārius (“bird keeper”)

   ‎rēte (“net”) + ‎-ārius → ‎rētiārius (“net fighter”)

Second-declension noun.

¹Found in older Latin (until the Augustan Age).

• Eastern Romance:
  • Aromanian: -ar m, -aru, -ariu
  • Romanian: -ar m, -ariu m
• Italo-Dalmatian:
  • Corsican: -aghju
  • Italian: -aio
  • Sicilian: -aru
• Western Romance:
  • Old French: -ier
    • Middle French: -er
      • French: -ier, -er
      • → English: -eer, -er
    • → Middle English: -er, -eer, -ere, -ier, -ir, -yr
      • English: -er (conflated with -ere)
      • Middle Scots: -er, -ar
        • Scots: -er (conflated with -ere)
    • → Italian: -iere
    • → Old Irish: -aire
      • Irish: -aire
      • Scottish Gaelic: -air
    • → Sicilian: -eri
  • Old Occitan: -ier
    • Catalan: -er, -era
    • Occitan: -ièr
    • Sicilian: -eri, -era
  • Rhaeto-Romance:
    • Friulian: -âr
  • Venetan: -aro, -ar, -er
  • West Iberian:
    • Old Leonese: -ero
      • Asturian: -eru
    • Old Galician-Portuguese: -eyro
      • Portuguese: -eiro
      • Galician: -eiro
    • Old Spanish: -ero
      • Spanish: -ero
• → Albanian: -ar
• → Asturian: -ariu
• → Catalan: -ari
• → English: -ary, -arian
  • → German: -är
• → Galician: -ario
• → German: -ar
• → Greek: -άρης (-áris)
• → Occitan: -ari
• → Polish: -ariusz
• → Portuguese: -ário
• → Proto-Germanic: *-ārijaz (see there for further descendants)
  • Gothic: -𐌰𐍂𐌴𐌹𐍃 (-āreis)
    • → Proto-Slavic: *-ařь (see there for further descendants)
• → Sicilian: -àriu
• → Spanish: -ario
• → Basque: -ari