electronic computer vs back up

electronic computer is a noun but back up is not a noun.

Word	Noun	Adjective	Verb	Adverb
electronic computer	Yes	No	No	No
back up	No	No	Yes	No

electronic computer (noun)	back up (noun)
a machine for performing calculations automatically

electronic computer (verb)	back up (verb)
	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