pay vs kick back

pay is a noun but kick back is not a noun.

Word	Noun	Adjective	Verb	Adverb
pay	Yes	No	Yes	No
kick back	No	No	Yes	No

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

pay (noun)	kick back (noun)
something that remunerates

pay (verb)	kick back (verb)
dedicate	spring back, as from a forceful thrust
bear (a cost or penalty), in recompense for some action	pay a kickback; make an illegal payment
convey, as of a compliment, regards, attention, etc.; bestow
give money, usually in exchange for goods or services
bring in
do or give something to somebody in return
cancel or discharge a debt
make a compensation for
discharge or settle
render
be worth it