pull away vs back up

pull away and back up both are verbs.

Word	Noun	Adjective	Verb	Adverb
pull away	No	No	Yes	No
back up	No	No	Yes	No

As verbs, back up is a hyponym of pull away; that is, back up is a word with a more specific, narrower meaning than pull away:

Other hyponyms of pull away include fall back, retreat, retrograde, back down, back off.

pull away (verb)	back up (verb)
pull back or move away or backward	establish as valid or genuine
	become or cause to become obstructed
	make a copy of (a computer file) especially for storage in another place as a security copy
	move backwards from a certain position
	give moral or psychological support, aid, or courage to