Roaring forties

Posted by Lotg (OZ) on August 18, 2004

Dini B asked about the Back 40, and that triggered this question from me.

The term Roaring Forties has two meanings for me - one is the 1940's, but the other is the winds.

I've had a bit of a surf, but can't find an answer. Why are those winds called the Roaring 40's? Does it mean 40 mph winds or something else?