Sit and its past-tense form sat, as well as set, settle, and seat, are cognates from Old English of the Latin verb sedere, meaning “sit.” The more or less disguised direct descendants of that term are listed and briefly defined in this post.
Words derived from a Latin verb stemming from sedere and meaning “sit beside” (originally pertaining to an official who assists a judge) include the verb assess, which means “estimate property value for taxation purposes” (the noun form is assessment); the adjective assiduous, meaning “showing great care”; and the noun assize, meaning “court session.” The noun and verb size, meaning “physical extent” and “arrange by size” respectively, among other things, is derived from assize.
To sedate is to calm or settle, the adjective sedate means “calm or settled,” the adjective sedative denotes “tending to calm or settle,” and a sedative is something that calms or settles, especially a drug. Sedan, originally the word for a chair attached to poles so it can be carried, was later applied to an enclosed automobile. Sedentary means “settled,” “physically inactive,” or “permanently attached.” (Sessile is a synonym for the latter sense, or means “directly attached to the base.”) Sederunt, taken directly from Latin, refers to an extended seated discussion. Sediment denotes material that settles to the bottom of a body of liquid, such as sedimentary rock; sedimentation is the process of formation of this type of rock.
Session, meaning “a meeting or series of meetings,” or “a period of instruction,” and séance, the word for a session at which communication with the spirit world is attempted, refer to sitting, while dissident, describing someone who disagrees with or opposes the status quo, literally means “one who sits apart.”
Reside means “dwell” or “live,” and preside means “govern” (literally, “sit before”); the noun forms are resident and president, and the adjectival forms are residential and presidential. Subside (literally, “sit down”) means “settle,” “sink,” “decrease,” or “descend,” and the act or condition of subsiding is subsidence. A subsidy, meanwhile, is a money grant; the literal meaning of the word, “sit near,” suggests the support a grant provides.
Obsess originally meant “besiege” but now refers to unrelenting attention to someone or something; the adjectival form is obsessive, and an instance of obsessing is an obsession. Siege itself means “a military blockade” and, by extension, “a serious or sustained attack.” Insidious, stemming from the idea of sitting in ambush, means “deceitful.”
Possess means “have and hold,” and the adjectival and noun forms are possessive and possession. To supersede is to replace or set aside; surcease, a descendant of supersede’s Latin forebear by way of Old French, means “cease” as a verb and, as a noun, refers to an act of desisting.
To beset is to harass or surround, or to ornament by setting or studding something with smaller objects, such as jewels in a crown. Similarly, to inset is to insert something into something else so that it can be seen, and an inset is something so treated, or a channel or the act of flowing in. Cosset, meaning “caress” or “pamper,” may come from an Old English word that means “cottage dweller” (in the sense of one who raises animals as pets).
See, the word for the location or authority of a high-ranking clergyman (distinct from see as it pertains to vision), is from a Latin word related to sedere that pertains to a seat.