I belive San Diego could also be translated back to Saint James or any of those other variants but there's some other odd step or two in between that I can't remember right now.

Ah it turns out that may not be true, though widely believed for the last couple of centuries:

https://en.m.wiktionary.org/wiki/Diego#Spanish

The one that shocked me the most was the number of different names that I associated with different countries that all turned out just to be variations on John.

Ivan, Ian, Euan, Hans, Sean, Jens, Juan, Yiannis, Giovanni, Evan, Ifan, Janko, Ivanko and many more

https://en.m.wikipedia.org/wiki/John_(given_name)#In_other_l...