Meaning

verb divulge confidential information or secrets

verb speak (about unimportant matters) rapidly and incessantly

originFrom Middle English blabben (“to talk foolishly”), perhaps from Middle English blabbe (“idle talk; talebearer”). Compare Middle English blaberen (“to blabber, babble”), Middle High German blabezen (“to stammer, babble”).

Etymology from Wiktionary, CC BY-SA 3.0