What is the meaning of “to work one’s fingers to the bone”?

When you say that you have been working or wearing your fingers to the bone, what you mean is that you have been working very hard for a long time. You have been putting in such an effort that you have managed to work the skin and flesh off your fingers. There is no skin or flesh left, only bones.

Example:I’ve been working my fingers to the bone trying to get the room ready for the guests.

Source: ‘Know Your English’ ( The Hindu) – May 14, 2007.