nutyoudaoicibaDictYouDict[nut 词源字典]
nut: [OE] Nut is a member of a restricted family of Indo-European ‘nut’-words, present only in the Germanic, Romance, and Celtic languages, that were derived ultimately from the Indo-European base *knu-, denoting ‘lump’. Latin nux (source of French noix, Italian noce, and Spanish nuez) came from an extended base *knuk-. Its derivative nucleus ‘nut, kernel’ has given English nucleus [18] and nuclear [19], and Vulgar Latin *nucātum is the source of English nougat [19].

The Germanic branch of the family, on the other hand, comes from an extended base *knut-, which has produced German nuss, Dutch noot, Swedish nöt, Danish nød, and English nut. The adjectival use of the plural, nuts, for ‘crazy’ dates back to the mid-19th century. It came from the metaphorical application of nut to ‘head’ – hence off one’s nut ‘deranged’, and in due course nuts.
=> nougat, nuclear, nucleus[nut etymology, nut origin, 英语词源]
nut (n.)youdaoicibaDictYouDict
"hard seed," Old English hnutu, from Proto-Germanic *hnut- (cognates: Old Norse hnot, Dutch noot, Old High German hnuz, German Nuss "nut"), from PIE *kneu- "nut" (cognates: Latin nux; see nucleus). Sense of "testicle" is attested from 1915. Nut-brown is from c. 1300 of animals; c. 1500 of complexions of women.

Meaning "crazy person, crank" is attested from 1903 (British form nutter first attested 1958; nut-case is from 1959); see nuts. American English slang sense of "amount of money required for something" is first recorded 1912. The nut that goes onto a bolt is first recorded 1610s (used of other small mechanical pieces since early 15c.). Nuts and bolts "fundamentals" is from 1960.