Solfeggio

Solfeggio was credited to Guido de Arezzzo (or Guido D'arezzo), but didn't start out with Do but Ut
The origin came from a Latin prayer to Saint John the Baptist by the monk and historian Paulus Diaconus (720-800AD)
Ut Queant Laxis
Resonare Fibris
Mira Gestorum
Famili Tuoram
Solve Polluti
Labii Reatum
Sancte Ioannes

Roughly translated means; "So that we your servants may freely sing of the wonders of your deeds, cleanse the guilt from our polluted lips, Oh Saint John"

Later, after Guido there was a 7th note added to the Sol-fa system.

Guido used the ascending hexachord chant for the basis for his teaching system.

Sol*feg"gio (?), n.[It., fr. solfa the gamut.] Mus.

The system of arranging the scale by the names do, re, mi, fa, sol, la, si, by which singing is taught; a singing exercise upon these syllables.

© Webster 1913.