Reconstruction:Proto-Celtic/eti

Etymology
From. The particle is currently the mainstream explanation for the difference between the absolute and conjunct forms in Old Irish and Old Welsh. However, other explanations of the absolute and conjunct have been proposed:
 * Cowgill and Kortlandt reconstruct this particle as and derive it from.
 * Roma and Budassi reconstruct subject pronouns instead of *eti as the clitic(s) that differentiated absolute and conjunct forms. They believe that their reconstruction also has the advantage of explaining the subject pronouns (like, , , etc.) not occurring as subjects of inflected verbs in Old Irish.
 * McCone opposes all forms of the “particle hypothesis” and claims the postulated sentence particle faces more difficulties than it solves and requires numerous dubious ad hoc phonological assumptions. Instead he postulates the generalization of topicalized clause-initial verbs whose final -i was shielded by other enclitics if present, and then homogenization of forms with and without following enclitics in this position.

Usage notes
This particle suffered severe transphonologization in Insular Celtic, after being contracted to *(e)s or possibly *eθ. It was placed as the second element of a sentence as an enclitic to the preceding word. The independent forms of Insular Celtic verbs arose from when *eti came after them, while the dependent forms arose whenever *eti did not do so.

In Old Irish, simple verbs folowed by this particle got to keep an extra syllable away from later apocope compared to the "plain" conjunct forms; contrast and its conjunct form  from.