According to wikipedia, earworm, a literal translation of the German Ohrwurm, is a term for a song stuck in one's head, particularly an annoying one. Use of the English translation was introduced by James Kellaris, an associate professor of marketing at the University of Cincinnati. His studies appeared to demonstrate that different people have varying susceptibilities to earworms, but that almost everybody has been afflicted at some time or another. So, earworm is a word for a SONG stuck in one's head. Is there a word for a thought, ANY thought, stuck in one's head? Or, was ALL thought an "earworm"?