I believe "Caesar" derives from the word "caesaries", which means "hair/curls/beard-hairs".
Romans at the time were using three names, the given name (Gaius), the family/clan name (Julius) and the cognomen (Caesar), which was originally a nickname that became hereditary to identify a particular branch of a family.
So, the emperor of Russia was called the tsar because Gaius Julius or one of his ancestors was nicknamed "Curly" or maybe "Beardy".
All the statues I’ve seen of him make his hair look not so curly, and they don’t show him having a beard. This open up the possibility that many royal titles are ultimately named after some Italian guy’s magnificent chest hair (which would be hard to capture in a statue).
I'm with you all the way, but I'm pretty sure cognomen had transitioned from nicknames to hereditary by Gaius Julius Caesar's time. Also, clean-shaven was a relatively new fashion in Rome -- Cicero, one of Caesar's political enemies and of the previous generation, had a speech complaining about how women these days liked pretty clean-shaven younger men, and not the robust full-bearded old patricians, like they should.
Another fun idea which has been proposed is that it’s an ironic nickname - so rather than ‘Baldy’ (which is you see busts of Caesar is certainly plausible) people called him or his ancestors ‘hairy’.
Another less popular theory is that it's from caesus which means to cut, which would be interesting because the cesarean section, also known as a C-section, was named after Caesar so it'd be a bit of circular definition.
>because Gaius Julius or one of his ancestors
Sextus Julius Caesar is the first Julii Caesares according to wikipedia. I just love that the term for all of them is Julii Caesares.
Romans at the time were using three names, the given name (Gaius), the family/clan name (Julius) and the cognomen (Caesar), which was originally a nickname that became hereditary to identify a particular branch of a family.
So, the emperor of Russia was called the tsar because Gaius Julius or one of his ancestors was nicknamed "Curly" or maybe "Beardy".