-mentum

Derived from the Latin suffix -menta in collective nouns like armenta (“herd, flock”). Latin -menta is from Latin -mentum (singular), from Proto-Italic *-məntom, from the plural Proto-Indo-European *-mn̥teh₂ (*-mn̥ + *-teh₂, plural of *-mn̥-to-).[1]

• (Classical) IPA^(key): /ˈmen.tum/, [ˈmɛn̪t̪ʊ̃ˑ]
• (modern Italianate Ecclesiastical) IPA^(key): /ˈmen.tum/, [ˈmɛn̪t̪um]

-mentum (plural -menta)

1. instrument, medium, or result of; e.g. monumentum

Second-declension noun (neuter).

• Balkan Romance:
  • Aromanian: -mintu
  • Romanian: -mânt
• Italo-Romance:
  • Italian: -mento
  • Sicilian: -mentu
• Padanian:
  • Friulian: -ment
  • Venetian: -mento
• Gallo-Romance:
  • Catalan: -ment
  • Franco-Provençal: -ment
  • Old French: -ment (see there for further descendants)
  • Old Occitan: -ment
    • Occitan: -ment
• Ibero-Romance:
  • Asturian: -mientu
  • Galician: -mento
  • Portuguese: -mento
  • Spanish: -mento, -miento
• Borrowings:
  • → Basque: -mendu
  • → Dutch: -ment
  • → English: -ment
  • → German: -ment
  • → Norwegian Bokmål: -ment

• http://etimologias.dechile.net/latin/?Sufijos
• Dictionnaire Étymologique de la Langue Grecque by Pierre Chantraine. Paris, 1968.