Screwed the Pooch - complete screwup.
I'd like to know the origin. The lame references/explanations I've found on the web typically guess that the origin is literal - carnal relations between human and dog - but this seems a simplistic, vulgar extension by folks with a limited appreciation for history and is not very logical. In the vacuum of authoritative comment on origins, I am left to guesswork. Wouldn't it make more sense that this phrase arose in the context of a hunter who accidentally kills his dog, thereby totally fucking up - an error anyone could make, but more likely someone careless, stupid, or lazy?