What is the origin of the idiom "buy the farm" and when to use it?

The idiom "buy the farm" is believed to have originated during or after World War II, particularly among U.S. military personnel. The phrase refers to the death of a soldier during combat, where the soldier's life insurance policy would pay out to his beneficiaries, enabling them to "buy the farm" with the insurance money. Over time, the expression evolved and is now used more broadly to describe someone's death, often in a casual or euphemistic manner.