S-tab translated to C-y on a mac?

[Daniel Pittman <daniel@rimspace.net>]

G'day.

I have recently needed to run Emacs 23.2 on a MacOS-X host, and have hit a
behaviour that I don't quite understand.  Specifically, Shift-Tab is
translated into Control-y, resulting in a "yank" operation.

Poking around I see a few bits and pieces relating to this, mostly seeming to
sit in the realm of VT100 translation and the like.

Since a quick search couldn't turn up, for me, an easy answer or an
understanding of the multiple layers of translation here (and given it is more
or less time for bed) I am asking your help:

Where should I go looking to most quickly cut through this morass and
understand what is translating my respectable C-tab into an unwelcome C-y?

Regards,
        Daniel
-- 
✣ Daniel Pittman            ✉ daniel@rimspace.net            ☎ +61 401 155 707
               ♽ made with 100 percent post-consumer electrons