costume vs fit out

costume is a noun but fit out is not a noun.

Word	Noun	Adjective	Verb	Adverb
costume	Yes	No	Yes	No
fit out	No	No	Yes	No

As verbs, fit out is a hypernym of costume; that is, fit out is a word with a broader meaning than costume:

Other hypernyms of costume include apparel, clothe, dress, enclothe, garb, garment, habilitate, raiment, tog.

costume (noun)	fit out (noun)
the attire worn in a play or at a fancy dress ball
the attire characteristic of a country or a time or a social class
unusual or period attire not characteristic of or appropriate to the time and place
the prevalent fashion of dress (including accessories and hair style as well as garments)

costume (verb)	fit out (verb)
dress in a costume	provide with clothes or put clothes on
furnish with costumes; as for a film or play	provide with (something) usually for a specific purpose