What is the origin of the idiom "in the dumps" and when to use it?

The origin of the phrase "in the dumps" is uncertain, but it is believed to have originated in the mid-19th century. It is commonly employed in informal conversations and everyday language to express one's own feelings or to empathize with others experiencing sadness or disappointment. This phrase can be used when discussing personal struggles, such as after a breakup, during a period of grief, or when feeling overwhelmed by life's challenges.