1704, "kernel of a nut;" 1708, "head of a comet;" from Latin nucleus "kernel," from nucula "little nut," diminutive of nux (genitive nucis) "nut," from PIE *kneu- "nut" (source also of Middle Irish cnu, Welsh cneuen, Middle Breton knoen "nut," Old Norse hnot, Old English hnutu "nut").
The general sense of "central mass or thing, about which others cluster or matter collects," is from 1762. In biology, "dense, typically rounded structure in a cell, bounded by membranes," from 1831. Later they were found to contain the genetic material. Modern meaning in physics, "positively charged central core of an atom," is from 1912, by Ernest Rutherford, though theoretical use for "central point of an atom" is from 1844, in Faraday.
"a small nucleus; the nucleus of a nucleus," 1839, from Latin nucleolus, literally "a little nut," diminutive of nucleus (see nucleus). Related: Nucleolar.
"formation of nuclei," by 1855, noun of action from nucleate (v.) "to form into or bring together as a nucleus" (1839), from Latin nucleatus, past participle of nucleare, from nucleus (see nucleus).
"sweetmeat made of almonds and other nuts," 1827, from French nougat (18c.), from Provençal nougat "cake made with almonds," from Old Provençal nogat "nutcake," from noga, nuga "nut," from Vulgar Latin *nucatum (nominative *nuca), from Latin nux (genitive nucis) "nut," from PIE *kneu- "nut" (see nucleus).
"the act of removing (a kernel, seed, tumor, etc.) from its cover or capsule," 1640s, noun of action from verb enucleate (1540s), from Latin enucleatus "pure, clean," past participle of enucleare "to lay open, explain in detail," literally "to remove the kernel from" (see ex- + nucleus). Mostly figurative in Latin (the notion is of getting at the "core" of some matter), and usually figurative in English until mid-19c. advances in science and medicine gave it a new literal sense.
1841, "of or like the nucleus of a cell," from nucleus + -ar, probably by influence of French nucléaire. General sense of "central" is from 1912. In atomic physics, "of or belonging to the nucleus of an atom," from 1914; of weapons deriving their destructive power from nuclear reactions, by 1945.
Hence nuclear energy (1930), nuclear physics (1933), nuclear war (1954). Nuclear winter was coined by U.S. atmospheric scientist Richard Turco but is first attested in article by Carl Sagan in "Parade" magazine, Oct. 30, 1983. Nuclear family, originally a sociologists' term, is first attested 1949 in "Social Structure," by American anthropologist G.P. Murdock (1897-1985). Alternative adjective nucleal is recorded from 1840, probably from French.
"the fruit of certain trees and shrubs which have the seed enclosed in a woody covering not opening when ripe," Middle English note, from Old English hnutu, from Proto-Germanic *hnut- (source also of Old Norse hnot, Dutch noot, Old High German hnuz, German Nuss "nut"), from PIE *kneu- "nut" (source also of Latin nux; see nucleus).
Sense of "testicle" is attested by 1915 (nuts). Nut-brown "brown as a ripe, dried nut" is from c. 1300 of animals; c. 1500 of complexions of women. The mechanical nut that goes onto a bolt is first recorded 1610s, from some fancied resemblance (nut was used of other small mechanical pieces since early 15c.). The figurative nuts and bolts "fundamentals" is by 1952. The American English slang sense of "amount of money required for something" is recorded by 1912.
Meaning "crazy person, crank" is attested from 1903; British form nutter is attested by 1958. Nut-case "crazy person" is from 1959; nut-house "insane asylum" is by 1929. For more on this sense, see nuts. In slang, nut also meant "fashionable or showy young man of affected elegance" [OED], 1904.