What is the origin of the idiom "lower than a snake's belly" and when to use it?

The idiom "lower than a snake's belly" is a figurative expression that likely originated from the association of snakes with negative qualities in various cultures. The phrase implies that a snake's belly, being close to the ground, is already considered low, and the person being referred to is even lower in character. It is used to emphasize extreme disapproval or contempt for someone's actions or character.