Slang
Alternative to openly calling someone a "Big Dick."
Grand = Big, Richard = Dick.
It is a corruption of the nickname used for Richard which is Dick. Likewise a Dick also was a slang term for a Detective (either Private or police) However being a corruption of an old Nickname this term is an insult.
Likewise this can be used to make a compound insult such as saying someone is being like Grand Richard's Cranium. That is calling someone a 'big dick head.'
The insult can be more condescending saying "Grande Resharde"as if you were using a French insult.
Example 1:
"Hey, I don't give a rat's ass what you think."
*"Just proves here who the Grand Richard is, now don't it?"*
Example 2:
"You missed a wonderful staff meeting. I got to meet the new boss. The guy HR is replacing James with intends to shake things up here. He is a Grand Richard for certain."
*"So your telling me he is a big dick?"*
"Throbbing, erect, and purple headed. I seriously think the guy has an ego the size of Texas."
Example 3:
"Stop acting like a Grand Richard."
*"WTF does that mean?"*
"YOU'RE BEING A BIG DICK!"
*"... >o<!"*