When you’re waiting nervously in anticipation of something, you’re on a kind of hook that may feel tender, but it’s not. The metaphorical hooks on which you find yourself are actually "tenterhooks."
A listener of ours came to this realization after trying to figure out where the phrase "tender hooks" comes from. He knew the meaning behind the phrase, but didn't know that "tender" should be "tenter."
Seeing as there are very few of us who are actually know what a "tenter" is, "tender" is not an uncommon reinterpretation. But how did we get here?
On his blog World Wide Words, Michael Quinion explains how "tenterhooks" go back to wool and cloth. After cloth was woven, it had to be cleaned and then carefully dried to prevent shrinking and creasing. This was accomplished by stretching the cloth over a wooden frame called a "tenter." The cloth was held in place with metal "tenterhooks" to keep it taut or tense.
As noted, if you're on "tenterhooks," you're in suspense or waiting for something impatiently, often with some fear. Your insides feel tense or strained, much like a piece of cloth stretched out with tenter hooks.
"Tenter" shows up in English in the 1400s and goes back to the same Latin word as "tent." The metaphorical phrase "to be on tenters" shows up in the 1600s, followed by "to be on tenterhooks" in the 1700s.
The expression "to be on tender hooks" is an eggcorn, which is what happens when we reinterpret something unfamiliar into something that makes sense to us. A classic example is the reinterpretation of "for all intensive purposes" to "for all intents and purposes."
Since very few people know what a "tenterhook" is, many people have reinterpreted it as a "tender hook." There are various explanations for this, including the idea that the metaphorical hooks are hitting tender places inside of our bodies, and that's why waiting is so painful.
In his usage guide, Bryan Garner traces the eggcorn "tender hooks" back to early 19th century American English. Professor Anne Curzan was able to find some recent examples of it in print, though she mostly found blogs and articles correcting people who say "tender hooks" instead of "tenterhooks." Shocking, we know.
