back up vs endorse

back up and endorse both are verbs.

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

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

back up (verb)	endorse (verb)
establish as valid or genuine	sign as evidence of legal transfer
become or cause to become obstructed	be behind; approve of
make a copy of (a computer file) especially for storage in another place as a security copy	guarantee as meeting a certain standard
move backwards from a certain position	give support or one's approval to
give moral or psychological support, aid, or courage to