Sunday 15th May 2016 6:10pm
To begin without ambiguity, the correct spelling is certainly NOBHEAD. Nobhead.
First of all let us consider Nob versus Knob in their roots and in the pejorative.
The first (and so most usual) use of Nob according to dictionaries is "a person of wealth or high social position". So by strict definition calling a person a 'nob' is somewhat complementary. That is until the social context gives rise to attitudes that consider such people negatively. At which point the term becomes pejorative and in so doing flips its meaning.
So where once a nob was a distinguished person, now they are distinguished within a reprehensible set. If you like, the best of the worst, the best at being most odious.
Nob also stands as slang for Penis. I expect in terms of considering that part of the male anatomy as the pre-eminent part, the part of highest worth and standing. It makes direct etymological sense. And nobhead follows.
There are some who will tell you that nob means head and therefore nobhead means "head head" - which they think makes no sense. But actually in these terms we can take it to mean head of all the nobs - that is head of the heads. Or in the pejorative, the best at being the worst of the worst.
Nobhead then works as a pejorative in several etymological dimensions.
However, the basic definition of Knob is "rounded lump on surface of something". Now, whilst parts of the male sexual organ clearly fit this description, the average unit as a whole doesn't - especially not in the enraged state. There is no clear, supportable, etymological connection between Knob and Penis.
In fact either form is probably now acceptable as the none pejorative use of Nob is somewhat arcane but nevertheless Nobhead claims prima facie status