Christian religious and cultural group that is the main branch of the Latter Day Saint movement started by Joseph Smith in the 1820s. They are very prominent in Utah.
In TRFZB, Frank Zappa wrote about playing in a pickup band at a Christmas dance held at a Mormon recreation hall.
"I didn't know anything about Mormons at the time, so, during a break when I lit up a cigarette, it was as if The Devil Himself had made a rare personal appearance. A bunch of guys who looked like they weren't ready to shave yet started flailing over to me and, in a brotherly sort of way, escorted my ass out the door. I knew I was going to love show business if I ever got into it."