How the hell does this even have any relation to dying..
John Kirsopp
Back when farmer’s sons were sent to fight in wars, the government made the promise that if their son died in the war, their family farm would be fully paid-off. Hence, if someone died, “they bought the farm”.
euphemism: 1. the substitution of a mild, indirect, or vague expression for one thought to be offensive, harsh, or blunt. 2. the expression so substituted: "To pass away" is a euphemism for "to die."