Second Line: the street dance that accompanies hot jazz music in New Orleans

Second Line for Jessie Hill
Originally uploaded by Chuck T.

Second line is a tradition in brass band parades in New Orleans, Louisiana. The term is also used for an associated traditional dance style, notes wikipedia.

Music is an important part of most public events in traditional New Orleans culture. Processions with music include the periodic parades of benevolent societies, social aid & pleasure clubs, such as Zulu, other Carnival krewes, and of course the famous funerals with music, often called "jazz funerals".

The "first line" of a funeral consisted of the people who were an integral part of the ceremony, such as the members of the club or krewe, or family and friends of the deceased. The "second line" originally referred to people who were attracted to the music.

To follow such processions because one enjoyed the music came to be known as to "second line" or to be "second lining." Uninhibited dancing at processions also came to be called second lining.

For uninihibited dancing, see the push-up like, worm-like undulating dance move performed by men on the dance floor or pavement called "popping a gator."

Thus we see that the roots of jazz are in a type of dance music.