One, quite famous, Roman surname is Caesar. Unlike the modern english pronunciation of his name, the pronunciation follows what you have written: Kaesar.

In Germanic this morphed into "Kaiser", which is the german word for "Emperor". I find it quite interesting how the status and power of this one man was so widely recognized, that his surname was already used during Roman times (and still is in the German language) as a title for someone holding utmost power. Originally, the name Caesar likely just meant "a hairy person".

Also the source of czar and tsar!

Actually, Caesar was not a surname (family name), it was more like a nickname. The name (using the modern spelling) was Gaius Julius.

I think it might derive more from Augustus' use of the name- he was the first Roman emperor, though Caesar did rule as dictator for a little while.

Augustus was Caesar’s heir, and the name was part of his inheritance.

The same way Gaius Julius received it as an inheritance from his forebears. OP is totally right that the name and its power emanates from Octavian’s prestige and domination of the Roman world for near half a century.

Yeah, but it didn't become a title until the Julio-Claudians started using it to designate their heirs. When Augustus took it on, it was just a powerful family name. Once the Julio-Claudians were finished, it was a title.

It seems overwhelmingly likely that when later emperors kept using it, they were referencing the dynasty that Augustus founded, not Julius Caesar personally.

https://en.wikipedia.org/wiki/Caesar_(title)#Sole_Roman_Empe...

For anyone who likes this sort of thing, the initial few episodes of the History of English podcast[1] is amazing. It dives into the history right from Proto-Indo European and in fact covers the Greek and Etruscan influences, and spends time speaking about the people and their culture.

[1] https://historyofenglishpodcast.com/