system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do different languages each have their own version of the same names?

Why is Joseph not Joseph everywhere? When did he become Giuseppe? Who decided that Guillaume should be William? When hearing a new name, why does a culture make its own version of it instead of letting every name stay at its root?
gpt
Names begin as a single name in a parent language like Latin and will be spread throughout the geographical area where that language is spoken (in the case of Latin, most of Western Europe.) However, languages change gradually over time, with speakers slowly but surely changing the pronunciation rules of individual letters/sounds. The interesting thing about those changes is that they tend to occur consistently across the entire language, instead of in small pockets. The names end up being pronounced differently because the descendent languages have changed how they pronounce the original sounds of the name. Often spelling used to change to match pronunciation, which introduces another way for names to drift. 

As far as names adopted from other languages: remember that languages do not share the same sounds as each other. Many languages employ sounds that speakers of other languages simply cannot say correctly. Thus, many names couldn’t be adopted directly even if the adoptive speakers wanted to do so. 

As to the idea of “why don’t they keep it the same?” — that’s treating a language like it’s a conscious entity. It’s not: a language is simply the sum total of everyone who speaks it. If everyone hears a certain pronunciation, they will follow suit. There is no overarching control over how the language changes.