I was going to post the question in GQ, but an Internet seach turned up the answer. I must share it, so here it is.
I’ve heard that procol harum is a Latin phrase, but I know Latin, and I could never figure out what it was supposed to mean. It’s been bugging me on and off for years. This site explains it. Procol harum may be ungrammatical Latin for “Procul his” (his is ablative plural of haec, harum is genative plural of haec), which means “far from these things.” A more convincing theory is that the band is named after a cat, Procol Harun.