Where does “cьsarь” come from?

cьsarь (Proto-Slavic) comes from Proto-Germanic kaisaraz, from Latin Caesar, from Latin caesaries, from Proto-Indo-European kéysero- — hair.

Ancestry of “cьsarь”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	kaisaraz	emperor
2	Latin	Caesar	Julius Caesar; emperor
3	Latin	caesaries	or hair
4	Proto-Indo-European	kéysero-	hair

cьsarь — Etymology, Origin & Word History | Etymology Explorer