Origin of a Cheer

Re “Sis Boom Ah!” (That Was Then, April 22): I was always under the impression that the sound of the cheer was to simulate the sound of a cannon going off: The “sis” was the sound of the fuse, the “boom” the powder exploding, and the “ah” the gases in the wake of the ball leaving the barrel. That’s why the cannon was always fired after a touchdown. I guess they don’t do that anymore.