h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I always thought it was "freeze the balls OFF a brass monkey", as in cold enough to make the iron triangle (the monkey) shrink, and make the cannon balls roll off. Any enligtenment anyone?

I'd always heard it as on, not off, but then I did a search on Google which turned up a researched page that claimed that it was a false etymology, rendering the whole point moot I guess. So much for that one.

As far as i'm aware the origine was as suggested. Although the triangle was made of brass, the cannonballs were made of iron.
In low temperatures, brass, being less dense than iron, contracts quicker and to a greater extent, forcing the iron balls out of the triangle