This linguistic term for saying the same word twice in succession to create a new phrase is "reduplication". (Alternative terms less commonly encountered include "duplication" or "doubling".)
It has many functions depending on which language you are speaking. In Malay, for example, it is how plurals are formed (orang = man, orang-orang = men).
You are correct that the term "epizeuxis" is used only for cases where repetition is used for emphasis or to intensify meaning ("Never never never give up!")