That may be a local slang term, but it will not make a Sporty tank, less of a Sporty tank.
Back to the bginnings, the 2 outer sides of fatbobs were cut and welded together with a filler up top, looked like a peanut, also known as axed Harley tanks, but you wont hear that so often..
Then Wassel came out with a similar tank, later copied by a Japanese company..and they look a lot like a peanut..
We for years here derisively, called them penis tanks, but that does not mnean they are in fact.. just a slang term..
Sometimes regional slang is plain wrong.. like on here.. see double butt bucket Touring seats, called King & Queen.. and its becoming common.. but its not correct..King & queen is a chopper seat with some sort of back on it..