What is the meaning of -ius?

Latinizing suffix

suffix for making genera eponymous of a male person

forming adjectives from nouns

found as an ending of most Classical Latin 'nomina gentilicia' (family names or surnames, shared by the members of a gens)

suffix for Latinizing surnames

nominative/accusative/vocative neuter singular of -ior

comparative degree of adverbs ending in -ō

the regular genitive singular suffix for most pronouns

Source: wiktionary.org