An Etymological Dictionary of the German Language/Annotated/plappern

by Friedrich Kluge

plappern, verb, Modern High German only, an onomatopoetic form of a lost stem, blab, which is also indicated by the equivalent Middle High German blępzen, Old High German blabbiȥôn, ‘to blab, babble’; allied to Modern High German (dial) and Dutch blaffen, ‘to bark, yelp,’ Alemannian plapen, English to blab.