dentiloquist

Etymology
From Latin dens (tooth) + Latin loqui (to speak).

Noun

 * 1)  Someone who speaks through clenched teeth.
 * 2) * 1834, letter from John Fawcett to Charles Matthews dated 10 March 1834, re-printed in Anne Jackson Mathews, Memoirs of Charles Mathews, Comedian, Volume IV, Richard Bentley (1839), page 183:
 * To add to my mumbling complaint, (for, you must know, I have been quite a dentiloquist,) I have an only sister on a visit to me, who has been alarmingly ill for some time.