The name "Big Dick Rob" can be a title given to any human or animal with a naturally gargantuan dong. The origins come from a man named Rob that had a large penis, he was given the nickname "Big Dick Rob" and the rest is history.
"Holy shit have you seen his cock Martha?"
"Yeah! He really is a Big Dick Rob"
Samuel: Last night I spent my big dick money on a one night stand with Sally.
John: Big dick money well spent right there.
Samuel: Let's just say that the economy in my pants inflated 69% over the past 24 hours.