hook and eye vs fixing

hook and eye and fixing both are nouns.

Word	Noun	Adjective	Verb	Adverb
hook and eye	Yes	No	No	No
fixing	Yes	No	No	No

As nouns, fixing is a hypernym of hook and eye; that is, fixing is a word with a broader meaning than hook and eye:

Other hypernyms of hook and eye include fastener, fastening, holdfast.

hook and eye (noun)	fixing (noun)
a kind of fastener used on clothing	the act of putting something in working order again
	the sterilization of an animal
	(histology) the preservation and hardening of a tissue sample to retain as nearly as possible the same relations they had in the living body
	restraint that attaches to something or holds something in place