Where does the term " hangdog " come from ?

Question

I know years ago that animals were sentenced to death by hanging.

Answer 1

that's absurd. it describes a person who has sad saggy features like actor geoffrey palmer or don knotts. looks  like a bloodhound or bassett dog

Answer 2

It refers to a person wearing a guilty expression on their face. The expression has nothing to do with executing animals--it is that when a dog has done something that disappoints his master, he'll hang his head and his tail in a way that suggests "Oh, I screwed up..."

People do the same thing when they know they've messed up and been caught at it.