[saalweachter]

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.

[bee_rider]

Hopefully nobody wrote down the true source of his nickname so I can plausibly continue believing…

[NeoTar]

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’.

[saalweachter]

Are you familiar with the Three Stooges?