Clarification: Starting at 3:18, we went through the radical for 脾 and 啤, and mentioned that the left part of 脾 is 月。However, technically, the radical is 肉 (flesh) and not 月 (moon). The reason why 肉 looks like 月 has to do with how Chinese writing evolved.

Further reading (external link): https://www.jianshu.com/p/99331f30fae0