Finnish word -us comes from Finnish -s

Detailed word origin of -us

Dictionary entry	Language	Definition
-s	Finnish (fin)	Forms ordinal numbers from cardinal numbers, or ordinal pronouns. (case suffix, colloquial, or, dialectal) (enclitic) Mainly in informal contexts: a particle appended to an interrogative suffix -ko/-kö of the verb conjugated (also -kö with the negation verb) in order to bring the conversation partner or a person outside the conversation, talked about, emotionally closer to the speaker, or to [...]
-us	Finnish (fin)	Forms nouns from verbs, describing an action or event.. Forms nouns, indicating resemblance or association.

Words with the same origin as -us