Shit has actually a strange history to it. At the beginning there was an online group by and for involuntary celibates. It was a place where people could come together and try to process their situation. The loneliness, the depression, etc.
Now comes the M. Night Shyamalan plot twist: The founder was a woman. They came up with „invcel“ as short for involuntary celibates. Which later turned into „incel“ because it sounded better.
So, things were going dandy and that group did some good to help people. After some time she left the group. Just moved on to other projects. With her leaving the site started to (for a lack of better words) fucking degenerate. The whole movement became what we all know and hate today.