back up vs confirm

back up and confirm both are verbs.

Word	Noun	Adjective	Verb	Adverb
back up	No	No	Yes	No
confirm	No	No	Yes	No

As verbs, confirm is a hypernym of back up; that is, confirm is a word with a broader meaning than back up:

Other hypernyms of back up include affirm, corroborate, substantiate, support, sustain.

back up (verb)	confirm (verb)
establish as valid or genuine	make more firm
become or cause to become obstructed	establish or strengthen as with new evidence or facts
make a copy of (a computer file) especially for storage in another place as a security copy	strengthen or make more firm
move backwards from a certain position	administer the rite of confirmation to
give moral or psychological support, aid, or courage to	support a person for a position