The origin of the word "upset" can be traced back to the Old English word "upsettan", which means "to overturn or overthrow". This word was used to describe physical actions, such as knocking something over or turning it upside down. Over time, the meaning of "upset" expanded to include emotional states and mental disturbances. In modern English, "upset" is commonly used to refer to feelings of distress, frustration, or anger, as well as to situations that cause such feelings.