Etymology of "dog-tired"

Posted by Eric Weis on October 12, 2000

I have been searching various on-line dictionaries for the derivation of
this phrase. It is amazing that such a commonly understood phrase is
not to be found in any reference I can think of.

What is the background of this phrase? Is there a reason it is not widely
found in dictionaries?

• Etymology of "dog-tired" ESC 10/12/00