yack away vs yap away

yack away and yap away both are verbs.

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

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

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

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