That's what I kind of suspected is it's something to do with the female reproductive system. I'm sure someone around here has a more definitive answer though.
Hmm I do not actually know what they are used for. I do know that some breeds are bred for a "single lobe/paunch," most though have a double...although with Chance, the CP gander...he doesn't seem to have one at all. I'm curious to read the answers here!