That Darth is a title, not a name. I mean, why the hell not? First of all, it’s a solid portmanteau (“Dark Lord of the Sith”). Second of all, maybe this is just me, but I think Darth is kind of a funny name, but works fine as a title. Also, despite what people say, there is nothing in the OT that would suggest this shouldn’t be the case.
Disagree. At least in terms of how Obi-wan refers to him which suggests he was called Darth before he turned to evil and that was his first name.
Actually, yes. He says something like “a young JEDI knight called Darth Vader.” Its use as a title in the prequels explicitly assigns it to Sith/evil people. So why a Jedi would be named Darth becomes odd.