This
derogatory term is a
combination of
the following words:
1)'(NIM)rod' --which is the name of one of Green Day's album and a very good word on its own.
2)'numb(SK)ull' --borrowed the SK and another very good word on its own.
3)'dimw(IT)' --the IT from dimwit--and another very strong and good adjective
and finally, just for emphasis...
4) '(R)etard' --well, enough said.
Therefore, as opposed to calling someone a nimrod, numbskull, dimwit, or retard, you can use the oh-so-fantastic word nimskrit!