Dunno. But I took it to mean jackass.
Jehosaphat?
Well, in one of the best known “Dirty Ernie” jokes, the R-word is “rat.”
"A big fing rat with a pk this long!"
Could also be a joking reference to the South Park film trailer (not the actual film):
Mr Mackey: Young man, did you just say the Q-word?
I knew it was a joke, but I am enjoying the “J-word” suggestions.
This is probably right, as he was in a class of gifted students. (Krelboynes? Crelboynes?)