overfatigue vs fatigue

overfatigue is not a noun while fatigue is a noun.

Word	Noun	Adjective	Verb	Adverb
overfatigue	No	No	Yes	No
fatigue	Yes	No	Yes	No

As verbs, fatigue is a hypernym of overfatigue; that is, fatigue is a word with a broader meaning than overfatigue:

Other hypernyms of overfatigue include fag, fag out, jade, outwear, tire, tire out, wear, wear down, wear out, wear upon, weary.

overfatigue (noun)	fatigue (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

overfatigue (verb)	fatigue (verb)
tire excessively	exhaust or get tired through overuse or great strain or stress
	lose interest or become bored with something or somebody