On Fri, 16 Apr 2004 16:26:28 GMT, Peggie Hall
wrote:

Doug Kanter wrote:
Well, sometimes it's a partial deck above a ship's main afterdeck. But
sometimes it's not. :-)

Nope..ALWAYS a raised afterdeck, high enough to prevent taking on water
over the stern that could, in a heavy following sea, swamp the boat and
even sink it...a condition--as you correctly noted--from the Latin,
referred to as being "pooped." Hence the name "poop deck" for a RAISED
afterdeck.

I think you have it backwards. Puppis to poop
deck, thence pooped. The OED finds the use
of poop (actually pouppe) for the stern of a
ship as early as 1489, but not until 1748 does
someone use the word, in an account of a ship's
voyage, to mean hit by a large following sea.
The OED is not clear as to when it was first
used as a modifier of deck, but I see citations
that clearly predate 1748.