What does Boxing Day have to do with boxing?
1919, from Cuban Spanish rumba, originally "spree, carousal," derived from Spanish rumbo "spree, party," earlier "ostentation, pomp, leadership," perhaps originally "the course of a ship," from rombo "rhombus," in reference to the compass, which is marked with a rhombus. The verb is recorded from 1932. Related: Rumbaed; rumbaing.
ballroom dance of Afro-Cuban folk-dance origin that became internationally popular in the early 20th century. Best known for the dancers' subtle side to side hip movements with the torso erect, the rumba is danced with a basic pattern of two quick side steps and a slow forward step. Three steps are executed to each bar. The music, in 44 time, has an insistent syncopation.