ar son

Etymology
Disputed; there are two Old Irish nouns, one meaning ‘sound; word, name’ (a borrowing from Latin ), and one meaning ‘prosperity, well-being’ (cognate with and ). The connection with was rejected by the Lexique étymologique de l'irlandais ancien, its authors unconvinced on semantic grounds. The Dictionary of the Irish Language associates the preposition with the first of these, suggesting the original meaning ‘at the sound of, by the word/name of’. Dinneen’s and Ó Dónaill’s dictionaries, on the other hand, associate it with the second, suggesting the original meaning ‘for the well-being of’. Randall Gordon, in his study of Old Irish verbal nouns, associates the phrase with neither word and proposes his own etymology connecting it with, from which is also derived. Cognate with 🇨🇬 in any case.

Preposition

 * 1) for, for the sake of because of
 * 2) on behalf of speaking or acting for