-óir

• -eoir (slender form)
• -itheoir (used after verbs in -igh)

From Old Irish, from Latin -or.

-óir m

1. -er; suffix appended to words to create an agent noun, indicating a person who does (or a thing that does) something.

   ‎bád (“boat”) + ‎-óir → ‎bádóir (“boatman”)

   ‎Béarla (“English”) + ‎-óir → ‎Béarlóir (“Anglophone, English-speaker”)

   ‎focal (“word”) + ‎-óir → ‎foclóir (“dictionary”)

   ‎loisc (“burn, scorch”) + ‎-óir → ‎loisceoir (“incinerator”)

• The form is -eoir when the stem ends in a slender consonant.
• All nouns in -óir are masculine nouns of the third declension;
• When attaching to verbs, may use the participle form as the stem:

  cuidigh (“help”), pp. ‎cuidithe + ‎-óir → ‎cuiditheoir (“helper”)

  tréig (“to abandon, desert”), pp. ‎tréigthe + ‎-óir → ‎tréigtheoir (“deserter”)

  tuismigh (“procreate”), pp. ‎tuismithe + ‎-óir → ‎tuismitheoir (“parent”)

  • or the verb stem:

    ‎úsáid (“use”) + ‎-óir → ‎úsáideoir (“user”)

    ‎imir (“play”) + ‎-óir → ‎imreoir (“player”)

    ‎modhnaigh (“moderate”) + ‎-óir → ‎modhnóir (“moderator”)