John Finnemore on the French horn/cor anglais:

"I was idly wondering why the cor anglais has a French name meaning ‘English horn’, and the French horn has an English name meaning… well, ‘French horn’. I looked it up, even though I knew there would just be some reasonable but rather dull explanation.

"There isn’t. There is a completely bonkers explanation, in both cases. Here’s the first.

"So. The cor anglais isn’t English, or French. But that’s nothing, because another thing it isn’t is… a horn. It’s basically an overgrown oboe, and it’s from Silesia. But being thin with a bulb on the end, it looks a little like the trumpets angels are shown playing in medieval art.

"Or at least it did to the Germans, who started calling it the Engellisches Horn, or angel’s horn. Can you see the hilarious misunderstanding that’s about to happen? Well, that happened. The Italians thought the Germans called it the English Horn, so they translated it to corno inglese. The French got it from the Italians, and called it the cor anglais. The British got it from the French, and presumably stared at it, thought ‘We can’t call that an English horn! It’s nothing to do with us, we’ve only just this minute seen one!’ …and I suppose decided just to keep the French name to save embarrassment.

"But that is rationality itself compared to what happened with the “French” horn.

"Right. The French horn. It isn’t French, or English… but it is a horn. So that’s something. (In fact, horn players just call it ‘the horn’, and they wish you would too, but they can’t make you.) This story is simpler than the cor anglais one, but even more gloriously stupid.

"The French were famous for making beautiful hunting-horn type horns: curly tubes that made a nice noise when you blew through them. Then the Germans came up with a more complicated horn with slides and crooks and valves and what-have-you. So British horn players started calling the horns they played in orchestras French Horns, to make it clear they were having nothing to do with those funny looking new German horns with all the bits hanging off them. But the thing is… slides and crooks and valves and what-have-you are a really good idea. You can play tunes with them and everything. So, before long, in a brilliantly British combination of ruthless pragmatism and equally ruthless face-saving, British horn players were playing German horns… but still calling them French horns.

"In summary then: the cor anglais, or English horn, is a Silesian oboe that the Italians thought the Germans thought was English, but the Germans actually thought looked angelic. Whereas the French horn is a German horn that the British called the French horn to distinguish it from the German horn… which is what it is.

"All clear? Good. Carry on."