I have written some posts in this thread about jazz dances, including the Black Bottom. In my post about the Black Bottom the implication is that "bottom" means "butt". However, Lynne Fauley Emery, author of Black Dance From 1619 to Today (Princeton: Princeton Book Publishers, Second Revised Edition; 1988;p 221) gives a different origin for the name of that dance:

"According to [Zora Neale] Hurston, one of the dances originating in a jook was the Black Bottom. This dance "really originated in the jook section of Nashville, Tennesse, around Fourth Avenue. This was a tough neighborhood known as the Black Bottom-hence the name"...

Source noted-Zora Neale Hurston, "Mimicy", in Nancy Cunard, Negro Anthology (London: Wishard and Co; 1934); p.44