autumn years vs eld

autumn years and eld both are nouns.

Word	Noun	Adjective	Verb	Adverb
autumn years	Yes	No	No	No
eld	Yes	No	No	No

As nouns, eld is a hypernym of autumn years; that is, eld is a word with a broader meaning than autumn years:

autumn years: (literary) the later years of one's life, especially after one has finished their career.
eld: a late time of life

Other hypernyms of autumn years include age, geezerhood, old age, years.

autumn years (noun)	eld (noun)
(literary) the later years of one's life, especially after one has finished their career.	a late time of life
	a time of life (usually defined in years) at which some particular qualification or power arises