The term "comma pump"

[Joseph Perhson, TD 472.19:]
>I have a question concerning the term "pump" as it applies to the
>"commadrift." What is the difference between the "comma pump" which,
>evidently, Paul Erlich kindly illustrated for me and the "diesis pump?"
>Am I to assume with the "diesis pump" the 1/1 doesn't "pump around" but
>another pitch does??
>And why is it called "pump?" This can't have any application to organ
>tuning terminology, can it?? It seems to imply that rather than just
>"drifting," a pitch is "forced."Please inform... I'm "pumped up"
>now...

I may be guilty of introducing the term "pump" in TD 79 (03-04-99). If
you play the sequence C-A-D-G-C... repeatedly, there is strong downward
pressure on the center of tuning, and I just think of it as a "pump"
which must be resisted to prevent some VERY strange sounds. I had been
wrestling with the "pump" before I joined the list (and I'm STILL
wrestling with it!).

I'll let Paul E. answer regarding the "diesis pump" and the nomenclature
to be used for the distant note.

JdL