###A type of Reduplication
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".)
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!")
For the case where reduplication is used to form a new meaning, I am not aware of a specific word. We could describe it as neologistic reduplication.
Reduplication has many functions depending on which language you are speaking. In English, it is very often epizeuxis. Interestingly, in Malay, for example, it is how plurals are formed (orang = man, orang-orang = men).
In English it can be used to to cute effect in creating words that might be considered kidspeak: mama, dada, nana, boo-boo, wee-wee, tum-tum, etc.
It is also quite common in English to form reduplicatives where one vowel changes: riff-raff, sing-song, ding-dong, tip-top, wishy-washy, dilly-dally, chit-chat, mumbo-jumbo, namby-pamby, roly-poly, and so on. These are usually considered to be a type of reduplication.