Origin

　　起源

　　The phrase pigs might fly or pigs may fly has been used in various forms since the 1600s, when it was said that pigs fly with their tails forward, used as a sarcastic remark something overly optimistic. The form when pigs fly is more common in America.

　　“猪会飞”这个短语从17世纪开始就以各种形式被使用，当时人们说“猪倒着飞”，用来讽刺一些过于乐观的话。“当猪都能飞”在美国更为常见。

　　Meaning: Something that will never happen or something is highly unlikely to happen

　　意思：永远不会发生的事情，或者不太可能发生的事情

　　Example Sentences

　　1. I asked my boss if I could go on a two month vacation, he said yes, when pigs fly!

　　我问我的老板我能不能度两个月的假，他说要是猪能飞就让我去。

　　2. I think he'll pay you back your money when pigs fly.

　　我想他会把你的钱还给你——当猪飞起来的时候。（绝不可能还你）

　　3. I think I'll start working on my project from tomorrow. Yes, when pig fly!

　　“我想从明天开始我的项目。”“是的，要是猪会飞话。”