Kevin  Durant is fighting back against a lawsuit claiming he stole the  nickname "Durantula" from a 1980s musician ... arguing that he didn't give  himself the moniker and doesn't even use it to make money.

As TMZ first  reported, the Oklahoma City Thunder star was  sued by guitarist Mark Durante, who claimed he had trademarked the  name and used it to sell merchandise long before KD came along.

But in  his response -- filed earlier this month in Illinois Federal Court -- Durant  claims the media and his fans have been calling him by the name his whole  career. Durant says he has NEVER used the name to sell merchandise ... so  Durante's lawsuit has no merit.

In addition, Durant claims that no one  would ever confuse him with Durante (who has played with the likes of Public Enemy, The Aliens and The Next Big Thing).

KD wants  the lawsuit tossed completely and wants Durante to cover his legal fees.

A judge has yet to rule.