In the UK nut slangily means head, and metaphorically it meant head. Just one aside note here.
It seems like it was originally from the sports, meaning that when one is very fond of some sport, so in that euphoria and joy he/she will dispense with reason!
Some would claim that being "out of one´s nut" would be like a figure of speech, comparing a fruit without its nut (comparing it with a human being head).
Well, there are plenty of others versions to the origin of it, feel free to pick one of your taste. Hee hee.http://www.etymonline.com/index.php?term=nutshttps://english.stackexchange.com/quest ... come-about