tenterhooks: [15] A tenterhook is one of a set of hooks used to hold cloth taut on a frame during manufacture, especially while its dries (tenter comes from medieval Latin tentorium, a derivative of Latin tendere ‘stretch’). The metaphorical use of on tenterhooks to mean ‘in a state of agonizing suspense’ dates from the mid- 18th century. [tenterhooks etymology, tenterhooks origin, 英语词源]
plural of tenterhook (late 15c.), "one of the hooks that holds cloth on a tenter," from tenter + hook (n.). The figurative phrase on tenterhooks "in painful suspense" is from 1748; earlier to be on tenters (1530s).