yap away vs yack

yap away is not a noun while yack is a noun.

Word	Noun	Adjective	Verb	Adverb
yap away	No	No	Yes	No
yack	Yes	No	Yes	No

As verbs, yap away and yack are synonyms defined as:

Other synonyms of yap away include jaw, rattle on, yack away.

yap away (noun)	yack (noun)
	noisy talk

yap away (verb)	yack (verb)
talk incessantly and tiresomely	talk incessantly and tiresomely