A few years ago, when a Lolita clothing brand released a print with French macarons on it, the Japanese fashion communities in the US got a little confused. "What are these? These aren't macaroons like we know them!" Eventually, a concensus seemed to be reached: macaroon (with two Os) referred to the coconut cookies that are just about everywhere during Passover and macaron (with one O) referred to the the light and airy cookie sandwiches.
As the French cookie became popular in the US, more people became curious about this treat now appearing in places such as Trader Joe's and becoming the featured treat in bakeries from coast to coast. Serious Eats put together a primer on the French cookie. And there's plenty of history out there. Slate lets us know how macaroon, macaron, and macaroni are related.
Still, when I hear macaroon, I think of the coconut cookies. And when I hear macaron, I think of the light, airy French treat. But if someone says "French macaroon" or a "coconut macaron" I'll probably be able to figure out what they're talking about.
I had hoped to make some coconut macaroons today, but having spent a large chunk of this last month traveling has caused life and all it's little chores to catch up to me. So I'm swamped right now. But I have all the ingredients for coconut macaroons and since National Chocolate Macaroon Day is coming up, I'll be making cookies then.