In grammar, the inessive case is a locative grammatical case. Wikipedia

Locative grammatical case for something that is inside of a container Wikidata

Noun case used to indicate location inside something. In English, this is usually expressed by the prepositions "in" or "inside", as in "inside the house". Languages that use the inessive case include Finnish, Hungarian, Estonian, Ossetian and Erzya. Wiktionary