1773, in the modern sense, from ventriloquy + -ism.
Entries linking to ventriloquism
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.
-ism
word-forming element making nouns implying a practice, system, doctrine, etc., from French -isme or directly from Latin -isma, -ismus (source also of Italian, Spanish -ismo, Dutch, German -ismus), from Greek -ismos, noun ending signifying the practice or teaching of a thing, from the stem of verbs in -izein, a verb-forming element denoting the doing of the noun or adjective to which it is attached. For distinction of use, see -ity. The related Greek suffix -isma(t)- affects some forms.
*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."