c. 1200, trone, "the seat of God or a saint in heaven;" c. 1300 as "seat occupied by a sovereign," from Old French trone (12c., Modern French trône), from Latin thronus, from Greek thronos "elevated seat, chair, throne," from suffixed form of PIE root *dher- "to hold firmly, support" (source also of Latin firmus "firm, steadfast, strong, stable," Sanskrit dharma "statute, law"). From late 14c. as a symbol of royal power. Colloquial meaning "toilet" is recorded from 1922. The classical -h- begins to appear in English from late 14c.
"to place on a throne, exalt to the seat of royalty," c. 1600, from en- (1) + throne (n.). Replacing enthronize (late 14c.), from Old French introniser (13c.), from Late Latin inthronizare, from Greek enthronizein. Also simply throne (v.), late 14c., from the noun in English. Related: Enthroned; enthroning.
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).
"a seat with a back, intended for one person," early 13c., chaere, from Old French chaiere "chair, seat, throne" (12c.; Modern French chaire "pulpit, throne;" the more modest sense having gone since 16c. with variant form chaise), from Latin cathedra "seat" (see cathedral).
Figurative sense of "seat of office or authority" c. 1300 originally was of bishops and professors. Meaning "office of a professor" (1816) is extended from the seat from which a professor lectures (mid-15c.). Meaning "seat of a person presiding at meeting" is from 1640s. As short for electric chair from 1900. Chair-rail "strip or board of wood fastened to a wall at such a height as to prevent the plaster from being scraped by the backs of chairs" is from 1822.
1580s, "that which is added," also "act of acceding" (by assent, to an agreement, etc.), from Latin accessionem (nominative accessio) "a going to, approach; a joining; increase, enlargement," noun of action from past-participle stem of accedere "approach, enter upon" (see accede). From 1640s as "act of coming to a position or into possession," especially in reference to a throne. Related: Accessional.