https://www.cnet.com/roadshow/news/desmo-valves-race-car-ducati-mercedes-motorcycle/

Desmo is short for desmodromic, and it refers to the way that a poppet

            valve
     inside of an engine is controlled. In almost every four-stroke piston engine, the valves are opened via a camshaft and closed by spring pressure which comes from a valve spring. It's a well-known system, it works, and it's pretty simple. That's why it's the dominant system in place today, even in high-strung race cars and bikes, but that wasn't always the case.

> The first mention of desmodromic valves comes from several 1896 patents by Gustav Mees, but it wasn't until around the 1910 mark that they were used with any real success in a marine engine that thanks to desmo, dual magnetos and dual overhead valves (itself something of a rarity in that time) was able to produce 300 horsepower.