E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Direct. A term in gunnery; when a cannon is so placed that the line of sight is parallel to the axis and horizontal, the discharge is point-blank, and is supposed to go direct to the object without a curve. In French point blanc is the white mark or bulls eye of a target, to hit which the ball or arrow must not deviate in the least from the exact path.
Now art thou within point-blank of our jurisdiction regal.Shakespeare: 2 Henry VI., iv. 7.