kit vs kit up

kit is a noun but kit up is not a noun.

Word	Noun	Adjective	Verb	Adverb
kit	Yes	No	Yes	No
kit up	No	No	Yes	No

As verbs, kit and kit up are synonyms defined as:

Other synonyms of kit include kit out.

kit (noun)	kit up (noun)
young of any of various fur-bearing animals
gear consisting of a set of articles or tools for a specified purpose
a case for containing a set of articles

kit (verb)	kit up (verb)
supply with a set of articles or tools	supply with a set of articles or tools