A Shawanahim is orinally the name of a board game designed to be impossible to complete.
The catchphrase for the game was as follows:
Shawana whats? Shawanahim's
Originating in a small garage in Norfolk, a Grimbent is a fond term for somebody who is a feckless wastrel, or a loveable but useless person.
You stupid Grimbent, go and sort that mess out.