Seance

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late 18th century: French séance, from Old French seoir, from Latin sedere ‘sit’.

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From French séance

etymonline

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seance (n.)

1789, "a sitting, a session," as of a learned society, originally in French contexts, from French séance "a sitting," from seoir "to sit," from Latin sedere "to sit" (from PIE root *sed- (1) "to sit"). Meaning "spiritualistic session in which intercourse is alleged to be held with ghosts of the dead" is recorded by 1845.