Just read about them recently and they were given this term by test pilots referencing the famous razor manufacturer. If you are flying an aircraft with Gillette wings, they are sharp enough to cut you. Why would wings be manufactured that are so sharp. It has to do with supersonic drag as explained here.
bi convex wing - Google Search
You can read some history about them here in the race to break the 'sound barrier'.
Bullet planes, fatal crashes – and the top secret British project to break the sound barrier first | National Geographic
Any further info is welcome.