Etymology
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ventriloquy (n.)
1580s, from Late Latin ventriloquus, from Latin venter (genitive ventris) "belly" (see ventral) + loqui "to speak" (from PIE root *tolkw- "to speak"). Related: Ventriloquial; ventriloquize.

Patterned on Greek engastrimythos, literally "speaking in the belly," which was not originally an entertainer's trick but rather a rumbling sort of internal speech, regarded as a sign of spiritual inspiration or (more usually) demonic possession. Reference to the modern activity so called seems to have begun early 18c., and by 1797 it was being noted that this was a curiously inappropriate word to describe throwing the voice.
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ventriloquist (n.)
1650s in the classical sense, from ventriloquy + -ist. In the modern sense from c. 1800. Ventriloquists in ancient Greece were Pythones, a reference to the Delphic Oracle. Another English word for them was gastromyth.
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*tolkw- 
Proto-Indo-European root meaning "to speak."

It forms all or part of: circumlocution; colloquium; colloquy; elocution; eloquence; grandiloquence; interlocution; interlocutor; locution; locutory; loquacious; loquacity; loquitur; magniloquence; magniloquent; obloquy; soliloquy; somniloquy; vaniloquence; ventriloquism; ventriloquy.

It is the hypothetical source of/evidence for its existence is provided by: Latin loqui "to speak;" Old Irish ad-tluch- "to thank," to-tluch- "to ask;" Old Church Slavonic tloko "interpretation, explanation."
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