You don't know siccum, meaning "you don't know anything," is an idiom common in the American Northwest. It's a shortened form of he doesn't know come here from sic 'em, as in a dog that doesn't know how to obey commands. This is part of a complete episode.
Listening to old podcasts of your show, I heard you discuss this expression and sort of expected you to point out that there is a related expression often used to denote confusion "he doesn't know if he's coming or going." At least it seems to me that these two might share some history.
My grandfather and his brothers n sisters used this phrase often. Our family came to southern wisconsin from the ohio Appalachians... one branch moved from Wisconsin to Newport Washington at the turn of the century where they ran a outfitters store...