I've long been aware of the word dentiloquist, one who speaks through the teeth -- it's in OED2 and gives Blount as the source (through dentiloquent). but along comes Jeffrey Kacirk in his 2010 Forgotten English calendar with dentriloquist, giving the same meaning. I think Kacirk must have conflated Blount's word with ventriloquist, which is also first cited in Blount's 1656 Glossographia.

unless, of course, Blount had it wrong. link