Where does “tsaari” come from?

tsaari (Finnish) comes from Russian царь, from Old East Slavic цьсарь, from Old East Slavic цѣсарь, from Proto-Slavic cěsařь, from Proto-Germanic kaisaraz, from Latin Caesar, from Latin caesaries, from Proto-Indo-European kéysero- — hair.

tsaari (Finnish): czar, tsar, tzar