Even if the Japanese name wasn't similar to Zubat, it's still clear that Woobat was intended to be the Zubat expy of Gen 5. Due to Black/White having only Gen 5 Pokemon for most of the game, they had to make a lot of expies of older Pokemon.
There are over 1,000 species of bat spread over every continent except Antarctica, making up about a fifth of all mammals. Woobat is no more an expy of Zubat than any other mammal-like Pokémon. If anything, there aren't enough bats.
The point is, the Zubat line were the only bat Pokemon for the first 4 generations. It was in Gen 5 that they added a new bat, Woobat. Gen 5 was intended to be a fresh start for the series, and as such, only Gen 5 Pokemon were available for a majority of the game. Because Zubat, who appeared in every other game to date, would no longer be available, they had to have a substitute annoying bat Pokemon that harassed you throughout caves.
http://meta289.deviantart.com/#/d4j1eby Fact: Things are so much better when taken at face value.