From Proto-Indo-European *h₁én. Matasović reconstructs *eni for the whole preposition, but since the preposition triggers a nasal mutation/eclipsis instead of a lenition in its descendants, a closed syllable may be reconstructed instead. However, the attested closed syllable could be explained by the theory of the early apocope of final /i/ in unstressed words, usually used to explain the rise of the absolute and conjunct inflection in Old Irish (by treating conjunct forms in the unstressed category).
- Proto-Brythonic: *ɨn
- Old Irish: hi, i
- ^ Matasović, Ranko (2009) Etymological Dictionary of Proto-Celtic (Leiden Indo-European Etymological Dictionary Series; 9), Leiden: Brill, →ISBN, page 116
- ^ Bisagni, Jacopo. (2012). The Origins of the Preterite of the Old Irish Copula and Substantive Verb: An Overview and New Ideas. Journal of Celtic Linguistics, 14(1), 1-29, p. 9