For your addition to weird word combinations in the vast world of english slang(vbg:) Pronunciation: 'nukul`hed
Synonyms: blockhead, bonehead, dunce, dunderhead, hammerhead, loggerhead, lunkhead, muttonhead, numskull,
Related Terms: addlebrain, addlehead, addlepate, beefhead, blockhead, blubberhead, blunderhead, bonehead, bufflehead, cabbagehead, chowderhead, chucklehead, clodhead, clodpate, clodpoll, dolthead, dullhead, dumbhead, dunderhead, dunderpate, fathead, jolterhead, jughead, lunkhead, meathead, muddlehead, mushhead, muttonhead, noodlehead, numskull, peabrain, pinbrain, pinhead, puddinghead, pumpkin head, puzzlehead, stupidhead, thickhead, thickskull, tottyhead
i think the mushhead is clipping for mushroomhead which runs close to "did you just fall off a turnip truck":)
which would lead to someone being called a "turniphead" which albeit strange then turns the word into a COMPLIMENT---ah the fun on language:)
Basically any vegetable or fattty substance or metal type object attached to head or skull makes the a word synonymous with KnucklHead list:)