What it means: When someone wakes up in a foul or grumpy mood for no reason at all. Where it comes from: The left side of the body is often associated with evil. So if you're ever watching a cartoon and the character is struggling with a moral dilemma, the devil will appear on their left shoulder and the angel on their right. So when society believed in superstition and evil spirits, they would push the left side of the bed up against the wall so that no evil demons could get in. This also meant that people had no option but to get in and out of bed from the right hand side.