stirrup vs stirrup iron

stirrup and stirrup iron both are nouns.

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

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

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

stirrup (noun)	stirrup iron (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