opening names

why do some people call  opening different names.

e.g. Benko Gambit is also known as Volga Gamit.

is one of the names more correct than another. I live in Denmark and I've seen a lot of players look at me if I Benko Gambit when they talk about Volga.

I've seen a lot of opening being called something in chessmaster and if I said the name in the club someone would say it is called something else.

I think in US and Europe I think it is kind of strange that we do not call opening the same. we have relatively the same chess schools??!

When the Benko was still new, there was an article in Chess Life & Review on what the Benko was and how it was different from the Volga.

I wonder if the difference is generally seen today.