What does the expression “with the tail between the legs” mean and Where does it come from?

“With the tail between the legs” is Fido for you.

Put him up against a toy terrier half his size and his tail promptly turns down under his belly.

Maybe he’ll even turn on his back, all four legs limp.

Brave dog!

The attitude of a cowardly or scared dog is so typical that we have long said of a thoroughly cowed, utterly abased, or dejected person that he stands or runs “with his tail between his legs.”