After I posted Ghost #7 Amsterdam I was alerted by phish.net user @westbrook to the origin of the “worm”. In an interview with High Times in 2002, Trey had this to say…
HT: Do you have a good tripping story?
TA: I usually don’t talk about my drug use, because I feel it’s a private thing, but, whatever, I’ll tell you this one story. When we were in Amsterdam, me and a friend took a couple of hits of acid and a hit of Ecstasy later on that night. We were walking around and I started imagining I was riding on this giant sandworm, because the roads kind of go up and down. I was picturing these huge sandworms, diving up out of the canals.
That’s where that phrase, “Back of the Worm,” came from. The next night in the middle of this crazy jam–one of these jams that get out of control and you feel like you’re not really playing, it’s just playing for you–I think I was yelling that and people started saying, “Back of the worm!” Then I read about it on a T-shirt six months later and I’m laughing ’cause I was with my friend who was with me that night in Amsterdam. We were just laughing that some guy was wearing a T-shirt with “Back of the Worm” on it.
You can find the entire article here Trey Interview with High Times