Off his rocker

Posted by James Briggs on January 04, 2002

I can find nothing in the Archives for this phrase. Today I had an email, part of which said:

"....anyway the reason for the e-mail is that I am sure I
have heard a proposed origin for the phrase 'off his rocker'... if memory
serves the idea was that it came from early days of steam engine particular beam engines....the beam engine rocks back and
forth and if it comes off the pivot (rocker) it goes mad, flailing about and
smashing up everything about it...."

What do others think of this? There's no origin offered in any of my reference books - in fact the phrase is only mentioned in two of them.