The other day I found some stuff I'd written inside the cover of a book years ago and had totally forgotten. It's the origins of do re mi (originally ut re mi) from a hymn by Guido d'Arezzo. You might find it interesting to read this wikipedia page on it.
It's a little more complicated than that - originally the scale began on A in the bass (and only went up as far as F, hence hexachord), then was lowered to G (known as gamma ut, whence the word gamut), and so on. I found it by accident originally in the dictionary under "Aretinian" (adjective pertaining to Guido d'Arezzo), probably during a failed search for Aretalogy, lol!