Some debate, but it seems that ! was used for factorial to replace another symbol that was less easy to print https://math.stackexchange.com/questions/802141/hi

Some debate, but it seems that ! was used for factorial to replace another symbol that was less easy to print https://math.stackexchange.com/questions/802141/history-of-notation#:~:text=used%20to%20denote%20the%20factorial,Christian%20Kramp%20chose%20%22!%22 https://math.stackexchange.com/questions/802141/history-of-n....