What it means: To work irregular hours. Night shift is when someone works during the night and sleeps during the day. Where it comes from: If people were going to be saved by the bell, it meant that the person who was buried could wake up at any time, unfortunately this didn't exclude the nighttime hours. So people were allocated night shifts or the graveyard shift to keep watch in the graveyard to listen out for the bells. However, people were also given this occupation when it was feared that vampires were rising from the grave to hunt during the night. This is why certain graveyards have watch towers as well as some iron cages that surround a grave.
