What is the origin of the idiom "like a bear with a sore head" and when to use it?

The idiom "like a bear with a sore head" originated from the behavior of bears when they are in pain or discomfort. Bears are known to become irritable and grumpy when they are suffering from physical ailments or injuries, and this behavior inspired the metaphorical use of the phrase. It is used to describe someone who is exceptionally irritable, bad-tempered, or easily angered. It suggests that the person is in a state of extreme irritability, similar to how a bear might react when experiencing physical pain or discomfort.