What is the origin of the idiom "banana republic" and when to use it?

The idiom "banana republic" was coined by American writer O. Henry in his 1904 book "Cabbages and Kings." It gained widespread usage and recognition after the book was published. O. Henry used the term to describe fictional countries in Latin America that were characterized by political instability, corruption, and economic dependence on a single export, which in the book's case was bananas. The term has since been used in discussions about developing nations or regions where a single export commodity, such as bananas, dominates the economy.