Where does “iys” come from?

iys (Ingrian) comes from Finnish -ittaa, from Finnish -ttää, from Proto-Finnic -ttadak, from Proto-Uralic -kta-.

Ancestry of “iys”, step by step

StepLanguageWordMeaning
1Finnish-ittaaVariant of -ttaa used with some bisyllabic stems
2Finnish-ttääFront vowel variant of -ttaa
3Proto-Finnic-ttadakCreates causative verbs from regular verbs,...
4Proto-Uralic-kta-—
Every word from Proto-Uralic -kta- →Every word from Finnish -ttää →Every word from Finnish -ittaa →