Wurdahuzdą: Proto-Germanic dictionary

suffix adj ja-stem forms denominal adjectives meaning ‘having, furnished with, characterized by, made of, or pertaining to’ the base noun From Proto-Indo-European *-yó-s, with Sievers-law allomorph *-iyó-s, the masculine nominative singular of the relational/possessive adjective suffix *-yó-/*-iyó-. The original sense was broadly ‘belonging to, connected with, characterized by, having’, whence Proto-Germanic denominal adjectives in *-(i)jaz, feminine *-(i)jǭ, neuter *-(i)ją, meaning ‘having X, characterized by X, pertaining to X’. Cognate with Latin-ius, Ancient Greek -ιος, and Sanskrit -य Fulk 2018: 213–14 Meier-Brügger 2003: 282–85 Ringe 2017: 326. Declension

The suffix varies as *-jaz /*-ijaz based on Siever’s Law: the basic *-jaz form is used after a “light” syllable (a short vowel followed by a single consonant), and otherwise, the form becomes *-ijaz.