footrest vs ottoman

footrest and ottoman both are nouns.

Word	Noun	Adjective	Verb	Adverb
footrest	Yes	No	No	No
ottoman	Yes	No	No	No

As nouns, footrest and ottoman are synonyms defined as:

footrest and ottoman: a low seat or a stool to rest the feet of a seated person

Other synonyms of footrest include footstool, tuffet.

footrest (noun)	ottoman (noun)
a low seat or a stool to rest the feet of a seated person	thick cushion used as a seat
	a low seat or a stool to rest the feet of a seated person