I don’t know what a mook is but I’ll take your word for it.
Scorcese’s early film “Mean Streets” has Robert DeNiro in it and he gets called a Mook and he’s peeved asking people “What’s a mook?”
https://www.urbandictionary.com/define.php?term=mook
1. a person of little social standing, one not worthy of respect.
“Mook is used as either a humorous (knucklehead) or derrogative (jerk) expression of humanistic imperfection or inappropriatness, such as to describe a person’s clumsiness or loudness.”
And one of his more recent roles was in a movie called Dirty Grandpa.
Thus Dirty Mook.
People say that DeNiro is a great actor but his classic roles are 25-30 years behind him.