African nation, named for the river that runs through it, which is from a Bantu word meaning "mountains" (i.e., the river that flows from the mountains). As an adjective, Congoese is native English (1797) but has been supplanted by Congolese (1900), from French Congolais.
Entries linking to congo
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.