It originated in the British Royal Air Force where an imperfectly-executed loop-de-loop would go 'pear shaped' instead of round as intended. Interestingly it th

It originated in the British Royal Air Force where an imperfectly-executed loop-de-loop would go 'pear shaped' instead of round as intended. Interestingly it then played off the British tendency for understatement so that something that meant 'a bit wonky' slid into meaning 'off the rails busted'.