The term nihilism was coined in 1817 by a German philosopher, and was promptly used so much that it lost its original purpose (irony intended, but I'm serious). Originally, it was used more to describe rationalism, but today it's more like something similar to existentialism. Anyway, the philosopher in question, Friedrich Jacobi, originally called it nihilismus, and he created that word from a portmanteau of the Latin word nihil, meaning nothing, and -ismus, which was just the German way of saying -ism (itself just a boring suffix with no semantic change in its etymology). Nihil comes from the prefix ne-, meaning "not" (from Proto-Indo-European ne, with the same definition and also the initial element in null, nothing, none, and nil), and the root hilum, which meant something like "trifle" (so, together combining to kind of mean "not in the least"). This has an obscure Proto-Semitic etymon.
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.