Where does “vesikäs” come from?

vesikäs (Ingrian) comes from Ingrian -kas, from Proto-Finnic -k'as, from Proto-Finnic -s, from Proto-Finno-Ugric -s.

Ancestry of “vesikäs”, step by step

StepLanguageWordMeaning
1Ingrian-kasForms adjectives describing an abundancy of a noun; -ful
2Proto-Finnic-k'asForms adjectives from nouns, indicating a...
3Proto-Finnic-sForms nouns
4Proto-Finno-Ugric-s—
Every word from Proto-Finno-Ugric -s →Every word from Ingrian -kas →Every word from Proto-Finnic -s →