What is the origin of the idiom "herd mentality" and when to use it?

The origin of the idiom "herd mentality" can be traced back to the concept of herd behavior observed in animals, particularly in groups of animals like sheep or cattle. It is used to refer to the instinctual behavior of animals to stick together and follow the movement or actions of the herd for safety and survival. This expression can be used in diverse settings, including social media trends, consumer behavior, political movements, and even decision-making processes.