From the day I started in my current position, back in 2009, I've used the term "Moodle shell" to refer to a Moodle "course." I never really asked why, I just accepted it. It seemed to make sense since we sometimes have "shells" for entire programs, or other non-academic purposes, where the term course seems inappropriate.
I've noticed that, even though I occasionally see others user this term, the word "shell" doesn't appear in the site glossary and there's no documentation referring to Moodle shells.
I'm just curious where this term came from and how prevalent is its use?
This is one of those things that make me go, "hmmm..."