nut
UK[nʌt]US[nʌt]
n
a dry fruit consisting of an edible kernel or meat enclosed in a hard or tough shell
n
a small piece of metal or other material with a hole through its center, designed to screw onto a bolt to secure something
n
(informal) a person who is very enthusiastic about or interested in a particular thing
n
(informal) a crazy or eccentric person
Etymology
the word 'nut' originates from the old english 'hnutu', which is related to the dutch 'noot' and german 'nuss'. these germanic terms can be traced back to the proto-germanic 'hnut-', a word of ancient lineage. while some connect it to the proto-indo-european root 'knew-', meaning 'lump' or 'clod', the semantic path is not entirely clear. the core concept of a hard-shelled seed has remained remarkably stable for millennia, with the mechanical and slang meanings developing much later as metaphorical extensions of this original, concrete object.
Analysis
the word 'nut' is a simplex word of old english origin. it is not productively formed from smaller, meaningful morphemes in modern english.
Examples
she cracked the walnut open with a nutcracker.
make sure the nut is tightened securely onto the bolt.
he's a real fitness nut, working out at the gym every single day.