Gloria in excelsis Deo
"Gloria in excelsis Deo" (Latin for 'Glory to God in the highest') is a Christian hymn known also as the Greater Doxology (as distinguished from the "Minor Doxology" or Gloria Patri) and the Angelic Hymn or Hymn of the Angels. The name is often abbreviated to Gloria in Excelsis or simply Gloria.
The hymn begins with the words that the angels sang in the annunciation to the shepherds of the birth of Jesus according to the nativity story in the Christian Bible, in Latin in the Douay-Rheims Bible. Other verses were added very early, forming a doxology.
An article by David Flusser links the text of the verse in Luke with ancient Jewish liturgy.