Seat
Middle English (as a noun): from Old Norse sæti, from the Germanic base of sit. The verb dates from the late 16th century.
wiktionary
From Middle English sete, from Old English sǣte and possibly (or simply cognate with) Old Norse sæti(“seat”), both from Proto-Germanic *sētiją(“seat”); compare Old English set(“seat”). Compare also Old High German gisazi (German Gesäß), Middle Dutch gesaete. Sense of "residence, abode, established place" likely derived from cognate Old English sǣte(“house”), related to Old High German sāza(“sedan, seat, domicile”).
etymonline
seat (n.1)
"thing to sit on; act of sitting," c. 1200, from Old Norse sæti "seat, position," from Proto-Germanic *sæt- (source also of Old High German saze, Middle Dutch gesaete "seat," Old High German gisazi, German Gesäß "buttocks"), from PIE root *sed- (1) "to sit." Meaning "posterior of the body" (the sitting part) is from c. 1600; sense of "part of a garment which covers the buttocks" is from 1835. Seat belt is from 1915, originally in airplanes.
seat (n.2)
"residence, abode, established place," late 13c., extended use of seat (n.1), influenced by Old French siege "seat, established place," and Latin sedes "seat." Meaning "city in which a government sits" is attested from c. 1400. Sense of "right of taking a place in a parliament or other legislative body" is attested from 1774. Old English had sæt "place where one sits in ambush," which also meant "residents, inhabitants," and is the source of the -set in Dorset and Somerset.
seat (v.)
1570s, "to be in a certain position" (implied in seated), from seat (n.2). Of diseases, in the body, from 1610s (hence deep-seated). Meaning "to cause to sit in a seat" is from 1610s, from seat (n.1). Related: Seated; seating.
