On one’s last legs 意為「(人) 垂死；瀕臨死亡；身體快要崩潰了」，而 on its last legs 意為「(物) 快用壞了；快要報廢了」。這個慣用語最早是出現在湯瑪斯‧米德爾頓 (Thomas Middleton)、威廉‧羅利 (William Rowley) 和菲利普‧馬辛格 (Philip Massinger) 聯合創作的悲喜劇 (tragicomedy)《舊法則》(The Old Law) 中。該劇首次發表於 1656 年，但一般認為在此時間的四十年前就已創作完成。
例句：
- I knew I was on my last legs, so I was very relieved to see the marathon’s finish line in the distance. (我知道我快累癱了，所以當我看到遠處的馬拉松終點線時，我就大大地放心了)
- Randy’s on his last legs—you should probably try to visit him in the hospital today. (蘭迪現在奄奄一息 － 你今天或許應該想辦法去醫院探視他)
- I’ve been cleaning house all day and I’m on my last legs. (我整天都在打掃房子，我快累死了)
- This computer is on its last legs. We have to get a new one. (這部電腦快掛了。我們必須買一部新的)
- I’ve had this smartphone for six years now, and it’s really on its last legs. (這支智慧型手機我已經用了 6 年了，現在的確是快要報廢了)