Note that the 7th tone of the scale is "see" (si). The 7th tone of the scale was given a syllable name from "St Iohannes", the last two words of the medieval plainsong hymn which was used as a memory device for the scale tones: UT queant laxis REsonare fibris MIra gastorum FAmuli tuorum SOLve polluti LAbiireatum Sanctu Iohannes, Of course UT was changed to DO later on, and the 7th scale tone was added.