For some time now, some of my on-line friends have advised me to provide a version of CassidySlangScam without the invective aimed at Cassidy and his supporters. In response to that advice, I am working on providing a glossary of the terms in Cassidy’s ludicrous book How The Irish Invented Slang with a short, simple and business-like explanation of why Cassidy’s version is wrong.
The word nut has a number of meanings in English slang. Typically, Cassidy makes no attempt to examine the different meanings and the relationship between them rationally and logically, simply jotting down a long list of different assorted meanings:
The nut hand is the most powerful hand in a poker game, also called the nuts; anything or anyone excellent; basic fixed expenses, overhead; (underworld) the minimum payoff to police to stay in business; a devoted enthusiast, an avid fan; someone with an acquired talent, skill or knowledge; a testicle; a head; a crazy person; al. to be very fond of someone or something.
Of course, the basic meaning of the word nut is a nut, as in a thing growing on a tree in a shell. The idea of a nut as something special or very good almost certainly derives from the nature of nuts as a delicacy, and apparently the meaning of nut/nuts as anything which is a source of pleasure or delight dates back to the early 17th century in English. The association between a head and a nut is logical enough, because they are both round things with a hard shell (that shell is known as a blaosc in Irish, which can mean both skull and the shell of a nut). This meaning also probably gave rise to nutty or nuts, or indeed a nut, as in an avid fan or a stalker, because people were described as being off their nut, just as they were described as being off their head. The physical resemblance of a walnut to testicles also explains the use of nuts for testicles. The American use relating to a sum of money required for something is also probably from the nut as in a thing growing on a tree, and dates back to the early twentieth century.
Cassidy seems to think (or at least, he claimed) that these words in English have nothing to do with the nuts on a tree. Rather, to him they are the word neart (pron. nyart). You can find the meanings of neart here:
As you can see, there is nothing to suggest that this is the origin of any of the meanings of nut or nuts in English slang.