gamut (n.) Look up gamut at
1520s, originally, "lowest note in the medieval musical scale," in the system of notation devised by Guido d'Arezzo, contraction of Medieval Latin gamma ut, from gamma, the Greek letter, indicating a note below A, + ut, the low note on the six-note musical scale that took names from corresponding syllables in a Latin hymn for St. John the Baptist's Day:
Ut queant laxis resonare fibris
Mira gestorum famuli tuorum
Solve polluti labii reatum
etc. Gamut came to be used for "the whole musical scale;" the figurative sense of "entire scale or range" of anything is first recorded 1620s. When the modern octave scale was set early 16c., si was added, changed to ti in Britain and U.S. to keep the syllables as different from each other as possible. Ut later was replaced by more sonorous do (n.). See also solmisation.