Name taken by the character Sokka from the TV show Avatar: The Last Airbender, when he and the others were undercover in the Fire Nation. Obviously, the name was made up on the spot.
While it certainly wasn't intended to be perverted, the fact that it is WANG Fire has caused the fandom to make many, many jokes about the name. The most common joke is to create a Chuck Norris-like persona for Wang Fire.
The only element Wang Fire bends is the element of surprise.
Wang Fire walked into a room, and all the women there were instantly pregnant. So were the men.