mutter vs kvetch

mutter and kvetch both are nouns.

Word	Noun	Adjective	Verb	Adverb
mutter	Yes	No	Yes	No
kvetch	Yes	No	Yes	No

As verbs, kvetch is a hypernym of mutter; that is, kvetch is a word with a broader meaning than mutter:

Other hypernyms of mutter include complain, kick, plain, quetch, sound off.

mutter (noun)	kvetch (noun)
a complaint uttered in a low and indistinct tone	(Yiddish) a nagging complaint
a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech	(Yiddish) a constant complainer

mutter (verb)	kvetch (verb)
make complaining remarks or noises under one's breath	express complaints, discontent, displeasure, or unhappiness
talk indistinctly; usually in a low voice