In 1911, physicist Ernest Rutherford did his famous "gold foil" experiment, where he determined that at the center of every atom is a small, dense, and positively charged mass. In 1912, he named this the nucleus. However, he wasn't the first person to use that word in reference to tiny particles; Michael Faraday actually coined the term in 1844, but only to refer a hypothetical central point of an atom, so Rutherford really gets the credit there. However, it goes deeper: the word has really been around in English since 1704 as a synoynm for "kernel of a nut", and Faraday just borrowed that because it seemed like a good analogy. However, this had the side effect of making the atomic definition become so popular that it largely drove out the more nutty meaning. Before then, the word was a diminutive of Latin nux, meaning "nut", and that in turn is from Proto-Indo-European kneu, with the same definition.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.