what does blue christmas mean

"Blue Christmas" is a song written by Billy Hayes and Jay W. Johnson in 1948 and popularized by Elvis Presley in 1964. The song is a melancholy lament about the sadness of the holiday season, when the holiday cheer and festive atmosphere only serve to highlight one's loneliness and heartbreak. It has since become a popular Christmas standard, often performed by many artists during the holiday season.