An omen (also called portent or presage) is a phenomenon that is believed to foretell the future, often signifying the advent of change.[2] People in ancient times believed that omens bring a divine message from their gods.[3]
These omens include natural phenomena, for example an eclipse, abnormal births of animals and humans and behavior of the sacrificial lamb on its way to the slaughter. They had specialists, the diviners, to interpret these omens
https://en.m.wikipedia.org/wiki/Omen