Tenterhooks were used as far back as the fourteenth century in the process of making woollen cloth. After the cloth had been woven it still contained oil from the fleece and some dirt. It was cleaned in a fulling mill and then had to be dried carefully as wool shrinks. To prevent this shrinkage, the wet cloth would be placed on a large wooden frame, a "tenter", and left to dry outside. The lengths of wet cloth were stretched on the tenter (from the Latin "tendere", to stretch) using hooks (nails driven through the wood) all around the perimeter of the frame to which the cloth's edges (selvages) were fixed so that as it dried the cloth would retain its shape and size.[1] At one time it would have been common in manufacturing areas to see tenter-fields full of these frames.
By the mid-eighteenth century the phrase "on tenterhooks" came into use to mean being in a state of uneasiness, anxiety, or suspense, stretched like the cloth on the tenter.