E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
I am on tenterhooks, or on tenterhooks of great expectation. My curiosity is on the full stretch, I am most curious or anxious to hear the issue. Cloth, after being woven, is stretched or tentered on hooks passed through the selvages. (Latin, tentus, stretched, hence tent, canvas stretched.)
He was not kept an instant on the tenterhooks of impatience longer than the appointed moment.Sir W. Scott: Redgauntlet, chap. xvi.