The name tailgate comes from the late 19th century when the trombone performers in Dixieland bands would often perform sitting on or over the "tailgate" of a horse-drawn wagon, facing backwards, while the other members of the band sat in the wagon bed in a parade or in a procession on the way to a funeral. By sitting on or over the "tailgate", the trombone player had ample room to move the trombone slide while performing frequent glissandos of the Dixieland jazz that often require the performer to extend the slide to its maximum length. Kid Ory is known as the King of the Tailgate Trombone and set the standard for this performance practice.
The trombone glissando is also known as a smear.
See also glissando; smear.