work tail off
work (one's) tail off
To work really hard (on or at something). I know you thought it was just a silly New Year's resolution, but I've been working my tail off at the gym! Sally and Jim work their tails off when we hold our consumer conference each year. I don't know what I'd do without them!
work one's tail offand work one's buns off; work one's ass off; work one's butt off
Inf. Fig. to work very hard. (Use caution with butt.) I worked my tail off to get done on time. You spend half your life working your butt off—and for what?
work one's tail off, to
To work very hard. This inelegant locution dates from the first half of the twentieth century. James Farrell used it in Studs Lonigan (1932–35): “This idea of sweating your tail off with work.” It also is put as to work one’s ass or butt off. See also break/bust one's ass.