work one's tail off

work one’s tail off

and work one’s ass off and work one’s buns off and work one’s butt off
tv. to work very hard. (Often objectionable.) You spend half your life working your butt off—and for what? I worked my buns off to get this done on time!
See also: off, tail, work
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.

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.
See also: tail, to, work
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer