Tenter

Tenterhooks are hooks in a device called a tenter. Tenters were originally large wooden frames which were used as far back as the 14th century in the process of making woollen cloth. After a piece of cloth was woven, it still contained oil from the fleece and some dirt. A craftsman called a fuller (also called a tucker or wa[u]lker) cleaned the woollen cloth in a fulling mill, and then had to dry it carefully or the woollen fabric would shrink. To prevent this shrinkage, the fuller would place the wet cloth on a tenter, and leave it to dry outdoors. The lengths of wet cloth were stretched on the tenter (from Latin tendere, meaning 'to stretch') using tenterhooks (hooked nails driven through the wood) all around the perimeter of the frame to which the cloth's edges (selvedges) were fixed, so that as it dried the cloth would retain its shape and size. In some manufacturing areas, entire tenter-fields, larger open spaces full of tenters, were once common.

By the mid-18th century, the phrase "on tenterhooks" came to mean being in a state of tension, uneasiness, anxiety, or suspense, i.e. figuratively stretched like the cloth on the tenter.

John Ford's 1633 play Broken Heart contains the lines: "There is no faith in woman. Passion, O, be contain'd! My very heart-strings Are on the tenters."

In 1690 the periodical The General History of Europe used the term in the modern sense: "The mischief is, they will not meet again these two years, so that all business must hang upon the tenterhooks till then."

In 1826, English periodical Monthly magazine or British register of literature, sciences, and the belles-lettres contained the line "I hope (though the wish is a cruel one) that my fair readers, if any such readers have deigned to follow me thus far, are on tenterhooks to know to whom the prize was adjudged." In a letter to his wife the same year, American educator Francis Wayland (waiting for his promised appointment as President of Brown University) wrote "I was never so much on tenter hooks before."

...
Wikipedia