hold on vs keep back

hold on and keep back both are verbs.

Word	Noun	Adjective	Verb	Adverb
hold on	No	No	Yes	No
keep back	No	No	Yes	No

As verbs, keep back is a hyponym of hold on; that is, keep back is a word with a more specific, narrower meaning than hold on:

hold on (verb)	keep back (verb)
be persistent, refuse to stop	prevent the action or expression of
stop and wait, as if awaiting further instructions or developments	hold back; refuse to hand over or share
hold the phone line open	secure and keep for possible future use or application
hold firmly
retain possession of