I enjoy word plays/puns and the like. When I was writing my story, I discovered that there was an antique farm tool (a kind of large sieve) called a "riddle". (One of the few extant uses of this in English today is "riddled with bullets", meaning full of holes like a sieve.) As soon as I heard such an implement existed, I made a point of 1. making one of these a key part of my plot and 2. putting it into my title, so that its double meaning would (as I like to think of it) reverberate nicely.
And I totally missed it!
Ok, in my own defense, I would like to say that I was blinded by the fact that there is an actual Sherwood ring in the story, the kind worn on the finger. But what I did NOT think about was that the whole story centers on Peaceable Sherwood, a super-competent British officer, assigned with the task of coordinating local Tories (in upstate New York) into a secret fighting force.
I believe that such a secret group of men is called a ring.
So this book's title, The Sherwood Ring, is a double-meaning word play exactly like what I did in The Riddle of Penncroft Farm.