O ( oh ) - v omhna.

ócaire (-í) - lowest grade of freeman without major skills, layman.

óenach - (esp. quarter year) assembly.

ogham - a Latin based rune-like alphabet of foreign origin.

Oíche Samhna - Samhain (qv) Night.

oidhe - doom, violent death (of an individual).

Oisín - poet, last of fianna.

ollamh - master, 7th rank (top) poet.

omhna - sessile-Oak (only), fiodh for the letter O, associated with, among other things, law, duty, honesty.

ór - gold.

ortha (-í) - charm, physical not verbal, or cliché verbal.

orthrus (usual form of complete folog n-orthrusa) - sick-maintenance, right of everyone to medical care (the longer term refers more specifically to long-term care).