An unexplained variant of 'tone,' from Greek 'tonos' (pitch) — 'tune' and 'tone' diverged from the same root within English.
A melody, especially a simple and easily remembered one.
An unexplained variant of 'tone,' from Old French 'ton,' from Latin 'tonus' (sound), from Greek 'tonos' (pitch, tension). How 'tone' became 'tune' in English is unclear — possibly dialectal. Key roots: tonos (Greek: "pitch, tension").