incoherency vs meaninglessness

incoherency and meaninglessness both are nouns.

Word	Noun	Adjective	Verb	Adverb
incoherency	Yes	No	No	No
meaninglessness	Yes	No	No	No

As nouns, meaninglessness is a hypernym of incoherency; that is, meaninglessness is a word with a broader meaning than incoherency:

Other hypernyms of incoherency include bunk, hokum, nonsense, nonsensicality.

incoherency (noun)	meaninglessness (noun)
nonsense that is simply incoherent and unintelligible	the quality of having no value or significance
lack of cohesion or clarity or organization	a message that seems to convey no meaning