Posted by David FG on June 08, 2005
In Reply to: Crazy as a loon posted by Alfredo DeFalco on June 08, 2005
: Crazy as a loon
I assume that you were asking for the origin of the phrase.
What in (English-speaking) Europe is called the Great Northern Diver is called in North America the Common Loon (a species of bird). It has a weird, haunting cry which presumably suggested to someone the howls of the insane. Hence, crazy as a loon.