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.
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.
word-forming element meaning "one who does or makes," also used to indicate adherence to a certain doctrine or custom, from French -iste and directly from Latin -ista (source also of Spanish, Portuguese, Italian -ista), from Greek agent-noun ending -istes, which is from -is-, ending of the stem of verbs in -izein, + agential suffix -tes.
Variant -ister (as in chorister, barrister) is from Old French -istre, on false analogy of ministre. Variant -ista is from Spanish, popularized in American English 1970s by names of Latin-American revolutionary movements.
<a href="https://www.etymonline.com/word/ventriloquist">Etymology of ventriloquist by etymonline</a>
Harper, D. (n.d.). Etymology of ventriloquist. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/ventriloquist