backlash vs fall out

backlash is a noun but fall out is not a noun.

Word	Noun	Adjective	Verb	Adverb
backlash	Yes	No	Yes	No
fall out	No	No	Yes	No

As verbs, fall out is a hypernym of backlash; that is, fall out is a word with a broader meaning than backlash:

Other hypernyms of backlash include come about, go on, hap, happen, occur, pass, pass off, take place.

backlash (noun)	fall out (noun)
an adverse reaction to some political or social occurrence
a movement back from an impact

backlash (verb)	fall out (verb)
come back to the originator of an action with an undesired effect	come to pass
	have a breach in relations
	drop out
	leave (a barracks) in order to take a place in a military formation, or leave a military formation
	come as a logical consequence; follow logically