octet vs eightsome

octet and eightsome both are nouns.

Word	Noun	Adjective	Verb	Adverb
octet	Yes	No	No	No
eightsome	Yes	No	No	No

As nouns, octet and eightsome are synonyms defined as:

Other synonyms of octet include octette.

octet (noun)	eightsome (noun)
a musical composition written for eight performers	a Scottish reel for eight dancers
eight people considered as a unit	eight people considered as a unit
a set of eight similar things considered as a unit
eight performers or singers who perform together
the cardinal number that is the sum of seven and one