what is the meaning of FATBOY on HARLEY DAVIDSON?

[Scarface]

I WOULD LIKE TO KNOW WHAT IS THE MEANING OF FAT-BOY ON HARLEY DAVIDSON I HAVE ALREADY HEARD A FEW DIFFERENT VERSION

 

[Andy Pandy]

It's not a fat girl!

 

[! c@n+ f33l my f@c3]

its a type of harley?

 

[harleyjim95]

it's a harley davidson model