muumuu (n.) Look up muumuu at Dictionary.com
also muu-muu, 1923, from Hawaiian mu'u mu'u, literally "cut off," name given to the local adaptation of the dresses given to Island women by early 19c. Christian missionaries "in the early days when a few flowers sufficed for a garment" [Don Blanding, "Hula Moons," 1930]. So called because the native style hangs from the shoulder and omits the high neck and the train.