stirrup iron vs stirrup

stirrup iron and stirrup both are nouns.

Word	Noun	Adjective	Verb	Adverb
stirrup iron	Yes	No	No	No
stirrup	Yes	No	No	No

As nouns, stirrup iron and stirrup are synonyms defined as:

stirrup iron and stirrup: support consisting of metal loops into which rider's feet go

stirrup iron (noun)	stirrup (noun)
support consisting of metal loops into which rider's feet go	support consisting of metal loops into which rider's feet go
	the stirrup-shaped ossicle that transmits sound from the incus to the cochlea