This expression came to mind as I was reading and reviewing The Astronauts Wives Club and thinking of the accidents that killed several astronauts. The Phrase Finder explains that the expression means “To die, particularly in an accident or military action.” The origin of the expression is uncertain, but explanations often include something to do with buying something at the cost of a serviceman’s life. The Phrase Finder suggests it might come from the fact a family receives an insurance payout when a serviceman is killed in action and that payout might be used to pay the family mortgage. However, it is admitted “…that we don’t have full evidence, that’s just speculation.”