On Sat, 12 Jul 2008 13:22:55 -0700, DGDevin wrote:

It has often been claimed that the "brass monkey" was a holder or storage
rack in which cannon balls (or shot) were stacked on a ship. Supposedly when
the "monkey" with its stack of cannon ball became cold, the contraction of
iron cannon balls led to the balls falling through or off of the "monkey."
This explanation appears to be a legend of the sea without historical
justification.

Ranks right up there with the "explanation" of 4' 8.5" gauge :-).