Webster's Revised Unabridged Dictionary · 1913

Blab

Blab (blab) , transitive verb

[Compare Old English blaberen, or Danish blabbre, German plappern, Gael. blabaran a stammerer; prob. of imitative origin. Compare also Blubber, v.]

To utter or tell unnecessarily, or in a thoughtless manner; to publish (secrets or trifles) without reserve or discretion; -- sometimes used with out. — Udall
And yonder a vile physician blabbing The case of his patient. — Tennyson

Blab , intransitive verb

To talk thoughtlessly or without discretion; to tattle; to tell tales.
She must burst or blab. — Dryden

Blab , noun

[Old English blabbe.]

One who blabs; a babbler; a telltale.
Avoided as a blab. — Milton
For who will open himself to a blab or a babbler. — Bacon