sis-boom-bahn.int.

Etymology: Imitative, representing the sounds associated with the launching of an explosive rocket: a hissing flight (siss n.; compare later siss int.), an explosion (boom n.¹), and an exclamation of delight from the spectators (ah int. and bah int. respectively). Compare earlier sky rocket n. 2 and see discussion at that sense.Compare similar earlier forms of cheer with slightly different first or second elements:1860 N.Y. Herald 25 Feb. 10/6 The boys enjoyed themselves..yelling out the ‘sky-rocket cheer’—a peculiar method of expressing emotion, in use amongst the Baltimore City Guard, and consisting of a sort of hip, booh, and final ah-ah.1860 Vanity Fair 10 Mar. 164/1 The City Guard turned out in force..And taught the Seventh something new—That cheer—the great Sky-Rocket, With its ch-h-h! boom! ah!1867 Ball Players' Chron. (N.Y.) 25 July 2/2 After cheers had been interchanged, and the Nationals had let off a ‘sky rocket’—namely a sort of finish to three cheers, with a ‘hiss—boom—ah!’—an adjournment was had to the clubhouse.