Other forms: tenterhooks
Long ago, a tenterhook was a special kind of hook that held drying cloth on a frame called a tenter. If someone is "on tenterhooks," it means they are in suspense — metaphorically hanging there, waiting for something.
Tenters and tenterhooks were commonly used from the fourteenth century, both as an important part of the process of weaving woolen fabric. Starting sometime in the eighteenth century, the phrase "on tenterhooks" came to mean "in suspense," the way a piece of cloth is suspended from tenterhooks on a tenter. So you might say that after entering a contest, you're on tenterhooks waiting to see if you'll win.