"Epizeuxis"
/From Wikipedia
In rhetoric, an epizeuxis is the repetition of a word or phrase in immediate succession, typically within the same sentence, for vehemence or emphasis.
From the OED
Etymology: modern Latin, < Greek ἐπίζευξις a fastening upon, < ἐπιζευγνύναι, < ἐπί upon + ζευγνύναι to yoke
Rhetoric.