In a state of agonising suspense, the expression dates from the mid-18th century but is preceded by an earlier expression ‘on tenters’ meaning the same thing that dates from the 1500s. ‘Tenters’ as a word dates from the 14th century and referred to the wooden frames used in the making of woollen cloth. After wool was woven, the cloth still contained oil and dirt from the fleece, which had to be washed out. The wet cloth would tend to shrink and crease so it had to be stretched on wooden frames or tenters while it dried. The hooks to which the cloth was fixed to these frames were called ‘tenter’ hooks. Thus by the 1500s, to be ‘on tenters’ meant to be in a state of agonising suspense, which evolved into tenterhooks by the mid-18th century.