offset (n.)

by c. 1200 as an emphatic form of Old English of (see of), employed in the adverbial use of that word. The prepositional meaning "away from" and the adjectival sense of "farther" were not firmly fixed in this variant until 17c., but once they were they left the original of with the transferred and weakened senses of the word. Meaning "not working" is from 1861.

Off the cuff "extemporaneously, without preparation" (1938) is from the notion of speaking from notes written in haste on one's shirt cuffs. In reference to clothing, off the rack (adj.) "not tailored, not made to individual requirements, ready-made" is by 1963, on the notion of buying it from the rack of a clothing store; off the record "not to be publicly disclosed" is from 1933; off the wall "crazy" is 1968, probably from the notion of a lunatic "bouncing off the walls" or else in reference to carom shots in squash, handball, etc.

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).