In my opinion, it can be thought in this way, these three man (sb) had elaborate(the action is finished) old Major's teaching (sth) into a complete system of thought(the goal, the result), to which(something happened to system of thought, which means the system of thought) they give the name of Animalism,( means to make a name Animalism for the system of thought ), sb did something into something, and give the thing a name, that is all!