Is that some clever way of telling if coins are fake?
Perhaps a coinsure is a chute that confiscates coins of the wrong weight...or even an app for telling if the Queen looks a smidgen too grumpy, or if the unicorn on the pound coin has the wrong number of horns.
Or perhaps it's a way of stopping coins from being eaten by parking meters; or a belt-mounted device for storing coins so we are never without the means of buying a desperately needed bottle of water (because, as the whole world keeps telling us, feeling a bit thirsty is practically, like, lethal. Yeah, right).
Coinsure...you know, that's a really interesting idea. I'd better look it up.
...coinsure. Here it is.
Coinsure: to insure jointly with another.
Oh. Co-insure. I get it.
Well, that was a massive disappointment, wasn't it.
Word Not To Use Without A Hyphen Today: coinsure. The co- bit is Latin, and is short for com- meaning, in this case, together. Insure probably comes from the Middle English assuren, to assure, and before that from the Latin sēcūrus, to secure.