go back on vs renege

go back on is not a noun while renege is a noun.

Word	Noun	Adjective	Verb	Adverb
go back on	No	No	Yes	No
renege	Yes	No	Yes	No

As verbs, go back on and renege are synonyms defined as:

Other synonyms of go back on include renege on, renegue on.

go back on (noun)	renege (noun)
	the mistake of not following suit when able to do so

go back on (verb)	renege (verb)
fail to fulfill a promise or obligation	fail to fulfill a promise or obligation