Simply put, feminism is not called humanism because the word humanism means something completely different from feminism. Feminism is a political movement and a philosophy of equality. According to the Merriam-Webster Learning Dictionary, humanism means “a system of values and beliefs that is based on the idea that people are basically good and that problems can be solved using reason instead of religion”.
There are some similarities and some differences between feminism and humanism and some think the historical negativity associated with the word feminism can be fixed by using the word humanism instead, but that will not work because the words do not mean the same thing.