Nominative singular ending *-ę reflects Early Proto-Slavic *-ēn, a regular reflex of a pre-form *-ent. Slavic nt-stems have no clear comparison in other Indo-European languages. It is usually compared to Latvian nouns in -ēn- which also often denote young animals with three possible theories of origin:
- Slavic suffix *-nt- originated in Proto-Slavic, by agglutination of the inherited Balto-Slavic *-n- and a secondary suffix *-t- of obscure origin.
- Balto-Slavic inflection exhibited ablaut, with Slavic generalizing normal grade *-en- and Baltic generalizing lengthened grade *-ēn-, with the origin of Slavic *-t- remaining unexplained.
- Balto-Slavic inflection already contained *-nt- suffix, retained in Slavic but with Baltic generalizing the nominoaccusative stem in *-ēn < *-ent.
- Forms nouns for young animals and other diminutives.