1701, "pleasure carriage," from French chaise "chair" (15c.), dialectal variant of chaire (see chair (n.)) due to 15c.-16c. Parisian swapping of -r- and -s-, a habit satirized by French writers. French chair and chaise then took respectively the senses of "high seat, throne, pulpit" and "chair, seat," but this was after chair had been borrowed into English in the older sense.

Originally a one-horse, two-wheeled carriage for two persons, later extended to other types of pleasure or travelling carriages. Chaise lounge (1800) is corruption of French chaise longue "long chair," with French word order, the second word confused in English with lounge.

1580s, "church of a bishop," from phrase cathedral church (c. 1300) "principal church of a diocese," a phrase partially translating Late Latin ecclesia cathedralis "church of a bishop's seat," from a specific early Christian use of classical Latin cathedra "a teacher or professor's chair," commonly "an easy chair (principally used by ladies)," also metonymically, as in cathedrae molles "luxurious women," from Greek kathedra "chair, seat, bench," also "exalted seat occupied by men of eminent rank or influence," from kata "down" (see cata-) + hedra "seat, base, chair, face of a geometric solid" (from PIE root *sed- (1) "to sit"). The Greek word was used in Old Testament and New Testament translations.

The English word was born an adjective, and attempts to force further adjectivization onto it in 17c. yielded cathedraical (1670s), cathedratic (1660s), cathedratical (1660s), after which the effort seems to have been given up.

also arm-chair, "chair with rests for the elbows," 1630s, from arm (n.1) + chair (n.). Another old name for it was elbow-chair (1650s). The adjectival sense, in reference to "criticism of matters in which the critic takes no active part," is from 1879.

1650s, "occupier of a chair of authority," from chair (n.) + man (n.). The meaning "member of a corporate body chosen to preside at meetings" is from c. 1730. Chairwoman in this sense is attested from 1699; chairperson from 1971.

gender-neutral alternative to chairman, chairwoman, by 1971, American English, from chair (n.) + person.

"woman who leads a formal meeting," 1699, from chair (n.) + woman.

also easy-chair, one designed especially for comfort, 1707, from easy + chair (n.).

child's seat, 1848, from high (adj.) + chair (n.).

Proto-Indo-European root meaning "to sit."

It forms all or part of: assess; assiduous; assiento; assize; banshee; beset; cathedra; cathedral; chair; cosset; dissident; dodecahedron; Eisteddfod; ephedra; ephedrine; ersatz; icosahedron; inset; insidious; nest; niche; nick (n.) "notch, groove, slit;" nidicolous; nidification; nidus; obsess; octahedron; piezo-; piezoelectric; polyhedron; possess; preside; reside; saddle; sanhedrim; seance; seat; sedan; sedate; (adj.) "calm, quiet;" sedative; sedentary; sederunt; sediment; see (n.) "throne of a bishop, archbishop, or pope;" sessile; session; set (v.); sett; settle (n.); settle (v.); siege; sit; sitz-bath; sitzkrieg; size; soil (n.1) "earth, dirt;" Somerset; soot; subside; subsidy; supersede; surcease; tanist; tetrahedron; Upanishad.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit a-sadat "sat down," sidati "sits," nidah "resting place, nest;" Old Persian hadis "abode;" Greek ezesthai "to sit," hedra "seat, chair, face of a geometric solid;" Latin sedere "to sit; occupy an official seat, preside; sit still, remain; be fixed or settled," nidus "nest;" Old Irish suide "seat, sitting," net "nest;" Welsh sedd "seat," eistedd "sitting," nyth "nest;" Old Church Slavonic sežda, sedeti "to sit," sedlo "saddle," gnezdo "nest;" Lithuanian sėdėti "to sit;" Russian sad "garden," Lithuanian sodinti "to plant;" Gothic sitan, Old English sittan "to sit."

Old English stol "seat for one person," from Proto-Germanic *stōla- (source also of Old Frisian stol, Old Norse stoll, Old High German stuol, German Stuhl "seat," Gothic stols "high seat, throne"), from PIE *sta-lo-, locative of root *sta- "to stand, make or be firm."(source also of Lithuanian pa-stolas "stand," Old Church Slavonic stolu "stool").

Originally used of thrones (as in cynestol "royal seat, throne"); decline in sense began with adoption of chair (n.) from French, which relegated stool to small seats without arms or backs, then to "privy" (early 15c.) and thence to "bowel movement" (1530s).