-ин-
Matasović R. Slavic Possessive Genitives and Adjectives from the Historical Point of View // The Grammar of Possessivity in South Slavic Languages: Synchronic and Diachronic Perspectives, Slavic Eurasian Studies No. 24. Sapporo, Japan: Slavic Research Center, Hokkaido University, 2011 , c. 1-12
"Slavic suffix *-in- could have been formed by ablaut (with the lengthened grade) and compared to Lith. -íena- in kárviena ‘beef’ (from kárvė ‘cow’), kiaulíenas ‘pork’ (from kiaulė ‘pig’). If this is correct, the PIE and the Balto-Slavic function of the suffix was not to indicate possession, but rather to derive qualitative adjectives from nouns"
с. 7-8
этимология