fatigue vs peter out

fatigue is a noun but peter out is not a noun.

Word	Noun	Adjective	Verb	Adverb
fatigue	Yes	No	Yes	No
peter out	No	No	Yes	No

As verbs, peter out is a hyponym of fatigue; that is, peter out is a word with a more specific, narrower meaning than fatigue:

Other hyponyms of fatigue include conk out, poop out, run down, run out, retire, withdraw.

fatigue (noun)	peter out (noun)
labor of a nonmilitary kind done by soldiers (cleaning or digging or draining or so on)
(always used with a modifier) boredom resulting from overexposure to something
temporary loss of strength and energy resulting from hard physical or mental work
used of materials (especially metals) in a weakened state caused by long stress

fatigue (verb)	peter out (verb)
exhaust or get tired through overuse or great strain or stress	use up all one's strength and energy and stop working
lose interest or become bored with something or somebody	end weakly