Don’t know the proper spelling but isn’t “numnutz” a term used by the 3 Stooges? I always thought the nuts part meant crazy, not a refererence to nuts.
The expression was originally “numbnut”, the nut in this case meaning “head”.
It was a synonym for numbskull.
Somewhere along the line the “s” was added, giving it a different, decidedly vulgar connotation.
BTW, I think “numbskull” was the word commonly used by the Three Stooges, although it’s been decades since I’ve watched a Three Stooges bit.