conga n.

type of Latin American dance, "usu. performed by several people in single file and consisting of three steps forward followed by a kick" [OED], 1935, from American Spanish, fem. of (danza) Congo "Congo (dance)" (see Congo); so called because it was assumed to be of African origin. As a verb by 1941. Related: Congaed; congaing.

Congo was used in the U.S. to form the names of dances associated with slaves from 1803. Congo dance is attested from 1823.