Fountain of Youth vs outpouring

Fountain of Youth and outpouring both are nouns.

Word	Noun	Adjective	Verb	Adverb
Fountain of Youth	Yes	No	No	No
outpouring	Yes	No	No	No

As nouns, outpouring is a hypernym of Fountain of Youth; that is, outpouring is a word with a broader meaning than Fountain of Youth:

Fountain of Youth: a fountain described in folk tales as able to make people young again
outpouring: a natural flow of ground water

Other hypernyms of Fountain of Youth include fountain, natural spring, outflow, spring.

Fountain of Youth (noun)	outpouring (noun)
a fountain described in folk tales as able to make people young again	a large flow
	the rapid and continuous delivery of linguistic communication (spoken or written)
	the pouring forth of a fluid
	a sudden rapid flow (as of water)
	a natural flow of ground water