Keep it under your hat

Q From Andrew Lewis: I was listening to a history programme on BBC Radio 4 a couple of days ago and the presenter was talking about the English longbow and how the archers were able to quickly detach their bow strings in the event of rain and would keep them dry under their hats. He suggested that it is from this that we get the expression keep it under your hat. I checked this out on your website but can find no reference to this expression. Just curious.

A Thank you for another splendid example of popular etymology to add to my substantial collection. English archers would seem to have accumulated more than their share of such stories, such as their supposed popular taunt pluck yew that was combined with a particular obscene gesture to show the enemy that they still possessed the fingers with which to pull their bowstrings.

As you have since written, there is evidence that English archers did keep their bow strings dry in this way. Juliet Barker writes in her book Agincourt: “According to the French chronicler Jean de Venette, they ‘protected their bows by putting the strings on their heads under their helmets’”. It seems that the story you mention has grown out of this practice.

There are two big problems with the story. To start with, how the meaning of the idiom developed is hardly obvious. How could the practice of keeping an essential part of one’s military equipment dry by putting it under one’s hat lead to a figurative idea of keeping something secret? The essence of the metaphor, of course, is that information or ideas that are “under the hat” are in the brain and so are secure from any interception.

Much more significantly, the tale fails on dating evidence. Keep something under one’s hat, meaning to keep something secret, is relatively modern, centuries later than medieval archers or ceremonial hats. It also seems to be American. This is the first example I’ve found in exactly that form:

If you do not wish to have your name as informant mentioned in connection with the matter, nor any thing done about it at all, say so; at any rate, tell us where you know of a producer who is engaged in the mixing business, and we will keep it “under our hat” if you say so.

Gleanings in Bee Culture, 15 Oct. 1892, 761/1. This was volume 20 of a well-known periodical, published every two weeks in Medina, Ohio.

There are earlier examples of under your hat from British English, but these are in slightly different senses, referring respectively to a person’s imagination, thoughts and skills:

But Adam was proof against this and several similar temptations, and when his neighbours asked how soon he was going to be wed, he would laugh and make some joking reply — say that he could not afford to keep a wife, that he preferred to keep his family under his hat, or that he could not find a lass to suit him.

The Old Factory, A Lancashire Story, by W B Westall, 1881.

Nuttie ... was taking in all these revelations with an open-eyed, silent horror. ... It was all under her hat, however, and the elder ladies never thought of her.

Nuttie’s Father, by Charlotte M Yonge, 1885.

The man whose estate lies under his hat need never tremble before the frowns of fortune.

What I Remember, by Thomas Trollope (the brother of Anthony), 1887.

I’ve unearthed two other stories that try to explain the idiom. One links it to President Abraham Lincoln, who famously wore a stove-pipe hat. He had the habit of keeping important papers in it, to the extent that he referred to it as his office. The other relates to the ceremonial swordbearer of the Lord Mayor of London, a post that can be dated to 1420, who keeps the key to the Lord Mayor’s seal of office in a special pocket in his hat.

Since we know that the expression is American and from a period only three decades after Lincoln’s presidency, it’s even possible the story about his hat is indeed the origin. But, in view of the English examples, I wouldn’t bet on it.