It is St. John's Eve. Tomorrow is the Feast of the Baptist. It was a tradition in the days of Christendom to have a bonfire in honor of the saint who was a "burning and shining light." (John 5:35) In some places, they still do; my father always had a bonfire in honor of the Birthday of the Baptist. In the Middle Ages, there were St. John carols (carols were not just for Christmas), dancing, and everyone would burn rubbish and old bones as a sign of the end of the old covenant. Houses would be decorated with St. John's Wort, and young girls would sleep with wildflowers under their pillows in the hope that they would dream of their future spouse. Fish Eaters, which has the details about the festivity, also discusses how the Vespers hymn for St. John's Day is the origin for "Do, Re, Mi:"
Another interesting thing about the Feast of St. John: the Breviary's hymn for this day, Ut queant laxis -- the hymn sung or recited during the blessing of the bonfire -- is the source of our names of musical notes -- Do, Re, Mi, Fa, So, La, Ti, Do. The hymn, attributed to Paulus Diaconus (Paul the Deacon, ca. A.D. 720-799), was noted by a monk to rise one note in the diatonic C-Scale with each verse. The syllables sung at each rise in pitch give us the names of our notes (the "Ut" was later changed to "Do" for easier pronunciation):Share
Ut queant laxis