From Proto-Finnic *kooppa, extended with -(a)s (compare dialectal koop, which was directly inherited). Cognates include Finnish kuoppa, Votic and Ingrian kooppa, Livvi kuoppu and Veps kop; possibly also Eastern Mari куп (kup, “bog”), Udmurt гоп (gop, “hole”) and Komi-Zyrian гӧп (göp, “small lake, hole”), although these are phonetically uncertain.
koobas (genitive koopa, partitive koobast)
| Declension of koobas (ÕS type 7/kallas, p-b gradation) | |||
|---|---|---|---|
| singular | plural | ||
| nominative | koobas | koopad | |
| accusative | nom. | ||
| gen. | koopa | ||
| genitive | koobaste | ||
| partitive | koobast | koopaid | |
| illative | koopasse | koobastesse koopaisse | |
| inessive | koopas | koobastes koopais | |
| elative | koopast | koobastest koopaist | |
| allative | koopale | koobastele koopaile | |
| adessive | koopal | koobastel koopail | |
| ablative | koopalt | koobastelt koopailt | |
| translative | koopaks | koobasteks koopaiks | |
| terminative | koopani | koobasteni | |
| essive | koopana | koobastena | |
| abessive | koopata | koobasteta | |
| comitative | koopaga | koobastega | |