set (v.)

Middle English setten, from Old English settan (transitive) "cause to sit; make or cause to rest as on a seat; cause to be put, placed, or seated;" also "put in a definite place," also "arrange, fix adjust; fix or appoint (a time) for some affair or transaction," and "cause (thoughts, affections) to dwell on."

This is from Proto-Germanic *(bi)satejanan "to cause to sit, set" (source also of Old Norse setja, Swedish sätta, Old Saxon settian, Old Frisian setta, Dutch zetten, German setzen, Gothic satjan), causative form of PIE *sod-, a variant of the root *sed- (1) "to sit." Also see set (n.2). It has been confused with sit (v.) at least since early 14c. 

The intransitive sense of "be seated" is from c. 1200; that of "sink down, descend, decline toward and pass below the horizon" (of the sun, moon, or stars) is by mid-13c., perhaps from similar use of the cognates in Scandinavian languages; figurative use of this is from c. 1600.

Many uses are highly idiomatic, the verb, like put, its nearest equivalent, and do, make, get, etc., having become of almost universal application, and taking its distinctive color from the context. [Century Dictionary]

The sense of "make or cause to do, act, or be; start, bring (something) to a certain state" (on fire, in order, etc.) and that of "mount a gemstone" are attested by mid-13c. That of "determine upon, resolve" is from c. 1300; hence be set against "resisting" (mid-14c.).

The sense of "make a table ready for a meal" is from late 14c. (originally "set a board on trestles to serve as a dining table"); that of "regulate or adjust by a standard" (of a clock, etc.) also is from late 14c.

In printing, "to place (types) in the proper order for reading; put into type," 1520s. From c. 1500 as "put words to music." From 1570s as "put (a broken or dislocated bone) in position." In cookery, plastering, etc., "become firm or solid in consistency" by 1736.

To set (one's) heart on (something) is from c. 1300 as "love, be devoted to;" c. 1400 as "have a desire for." To set (one's) mind is from mid-15c.; transitive set (one's mind) to "determine to accomplish" is from late 15c. To set (something) on "incite to attack" (c. 1300) originally was in reference to hounds and game. To set an example is mid-14c. (set (v.) in the sense of "present" is from late Old English). The notion of "fix the value of" is behind old phrases such as set at naught "regard as nothing."

To set out is from c. 1300 as "display (for sale);" to set up shop "commence doing business" is from c. 1400.

late Old English, sett, "appointed or prescribed beforehand;" hence "fixed, immovable, definite;" c.1300, of a task, etc., "imposed, prescribed;" past participle of setten "to set" (see set (v.)). By early 14c. as "ready." By 14c. with adverbs, "having a (specified) position, disposition, etc.;" by late 14c. as "placed, positioned;" to be set "be ready"

By 1510s as "formal, regular, in due form, deliberate;" 1530s as "placed in a setting, mounted." By c. 1600, of phrases, expression, etc., "composed, not spontaneous" (hence set speech, one planned carefully beforehand). By 1810 of the teeth, "clenched." The meaning "ready, prepared" is recorded from 1844.

By 1844 in reference to athletes poised to start a race, etc., or their muscles, "have or assume a rigid attitude or state." The exact phrase Get set! in the procedure of sprinting (after on your marks) is attested by 1890. A set piece, in theater, is "piece of free-standing scenery only moderately high, representing a single feature (such as a tree) and permitting more distant pieces to be seen over it" (by 1859); also, in the arts, "a painted or sculptured group" (1846).

"collection of matching things," mid-15c., sette, sete, earlier "religious sect" (late 14c.), in part from Middle English set, past participle of setten (see set (v.)) and in part from Old French sette, sete "sequence," a variant of secte "religious community," from Medieval Latin secta "retinue," from Latin secta "a following" (see sect).

Skeat first proposed that set (n.), in the sense of "a number of things or persons belonging together" ultimately was a corruption of the source of sect, influenced by set (v.) in subsequent developments as if meaning "a number set together." Thus this noun set was in Middle English earliest in the sense of "religious sect," which also likely developed some modern meanings, such as "group of people" (mid-15c.), especially "persons customarily or officially associated" (1680s); "group of persons with shared status, habits, or affinities" (1777).

The meaning "a number of things having a resemblance or natural affinity; complete collection of pieces to be used together" is by 1560s. Hence, "collection of volumes by one author" (1590s), "complete apparatus for some purpose" (1891, of telephones, radio, etc.).

Meaning "group of pieces musicians perform at a club during 45 minutes" (more or less) is from c. 1925, though it is found in a similar sense from 1580s. Set-piece is from 1846 as "grouping of people in a work of visual art;" from 1932 in reference to literary works.

The word sett is a variant, preserved in old law and "now prevalent in many technical senses" [OED].

Egyptian god, from Greek Seth, from Egyptian Setesh.

"act of setting; state or condition of being set" (originally of the sun or another heavenly body), mid-14c., from set (v.) or its identical past participle. Old English had set "seat," in plural "camp; stable," but OED finds it "doubtful whether this survived beyond OE." Compare set (n.1).

Disparate senses collect under this word because of the many meanings given the verb. The sense of "manner or position in which something is set" is by 1530s, hence "general movement, direction, drift, tendency, inclination" (of mind, character, policy, etc.), by 1560s.

The meaning "permanent change of shape caused by pressure; a bend, warp, kink" is by 1812; that of "action of hardening," by 1837. Hence "action or result of fixing the hair when damp so that it holds the desired style" (1933).

"Something that has been set" (1510s), hence the use in tennis, "set of six games which counts as a unit" (1570s) and set-point "state of the game at which one side or player needs only one point to win the set" (by 1928).

The theatrical meaning "scenery for an individual scene in a play, etc.," is by 1859, from the past-participle adjective. It later was extended in movie and television production to the place or area where filming takes place.

Set (n.1) and set (n.2) are not always distinguished in dictionaries; OED has them as two entries, Century Dictionary as one. The difference of opinion seems to be whether the set meaning "group, grouping" (here (n.2)) is a borrowing of the unrelated French word that sounds like the native English one, or a borrowing of the sense only, which was absorbed into the English word.