From Old Irish ar aí (“on account of, because of; as regards, in the matter of; for (the sake of)”).
ar aoi (plus genitive, triggers no mutation)
- in regard to, on account of
- "aoi" in Foclóir Gaeilge-Béarla, An Gúm, 1977, by Niall Ó Dónaill.
- “3 aí” in Dictionary of the Irish Language, Royal Irish Academy, 1913–76.