Emily Dickinson Lexicon

BLAB, v.t. [W. llavaru, to speak; D. labbery, prattle; Ir. clabaire, a babbler; labhraim, to speak; Chaucer, labbe, a blabber.]

1. To utter or tell in a thoughtless manner; to publish secrets or trifles without discretion. It implies, says Johnson, rather thoughtlessness than treachery, but may be used in either sense. – Dryden.
2. To tell, or utter, in a good sense. – Shak.