That's a bit different. It's possible that some early Unix machines had actual drum devices for storage or swap (did any of them?), but the /dev/drum device is what Clem says it was.
It's funny, I just happened across this a couple of days ago when I went looking for the `hier.7` man page from 4.4BSD-Lite2:
The claim is that it came from 3.0BSD. Why was it called drum? I imagine that's historical license coupled with grad student imagination, but I'm curious if it has origin in actual hardware used at UC Berkeley. Clem, that was roughly your era, was it not?
- Dan C.