Euphemism treadmill.
I always thought it was interesting how the term "president" began to proliferate very quickly after the US empire got big enough.
I think Caesar in particular is more interesting. The original Latin pronunciation is (somewhat disputed, being a dead language and all) likely something along the lines of Kai-tzar. Western Europe emphasized the first syllable, leading to king, while Eastern Europe emphasized the second syllable, leading to tzar.
This also reveals specific linguistic differences in how language works. English to a great extent, and other romance languages to a lesser extent, usually have the accent on the first syllable of the word, while eastern european languages have a lot more variety in which syllable of the word is emphasized.