Reconstruction:Proto-Celtic/-om

This Proto-Celtic entry contains reconstructed terms and roots. As such, the term(s) in this entry are not directly attested, but are hypothesized to have existed based on comparative evidence.

Proto-Celtic

Suffix

*-om n

Forms action nouns from e-grade (and sometimes zero-grade) roots corresponding to prefixed verbs.
‎*dīwed- + ‎*-om → ‎*dīwedom (“end”) (cf. *dīwedeti (“to stop”))

‎*uɸobey- + ‎*-om → ‎*uɸobeiyom (“blow, injury”) (cf. *binati (“to strike, beat”), a zero-grade formation)

Inflection

Neuter o-stem
	singular	dual	plural
nominative	*-om	*-ou	*-ā
vocative	*-om	*-ou	*-ā
accusative	*-om	*-ou	*-ā
genitive	*-ī	*-ous	*-om
dative	*-ūi	*-obom	*-obos
locative	*-ei	*?	*?
instrumental	*-ū	*-obim	*-ūis

Usage notes

Only prefixed verbs can use this suffix to make their verbal nouns. Simple, unprefixed verbs must use a different suffix or formation, even if it has related prefixed verbal nouns in -om.
Due to extensive final syllable apocope, the suffix phonetically vanished in all Insular Celtic descendants. By Old Irish, the only traces of the suffix are its mutational effects and the resulting verbal nouns' apparent lack of a derivational suffix. The loss of the neuter further incinerated these last traces of the suffix.