on (prep., adv.)

Middle English aboute, from Old English abutan (adv., prep.), earlier onbutan "on the outside of; around the circumference of, enveloping; in the vicinity of, near; hither and thither, from place to place," also "with a rotating or spinning motion," in late Old English "near in time, number, degree, etc., approximately;" a compound or contraction of on (see on; also see a- (1)) + be "by" (see by) + utan "outside," from ut (see out (adv.)).

By c. 1300 it had developed senses of "around, in a circular course, round and round; on every side, so as to surround; in every direction;" also "engaged in" (Wist ye not that I must be about my Father's business?), and gradually it forced out Old English ymbe, ymbutan (from PIE root *ambhi- "around") in the sense "round about, in the neighborhood of."

From mid-13c. as "in the matter, in connection with." From early 14c. as "in partial rotation, so as to face in a different direction." From late 14c. as "near at hand, about one's person." "In a circuitous course," hence "on the move" (late 13c.), and in Middle English "be about to do, be busy in preparation for," hence its use as a future participle in (to be) about to "in readiness, intending." Abouts (late 14c.), with adverbial genitive, still found in hereabouts, etc., probably is a northern dialectal form.

To bring about "cause or effect" and to come about "happen" are from late 14c. About face as a military command (short for right about face) is first attested 1861, American English.

Middle English above, aboven (also aboun in northern dialects, abow in southwestern dialects), from Old English abufan (adv., prep.), earlier onbufan "above, in or to a higher place, on the upper side; directly over, in or to a higher place than," a contraction or compound of on (also see a- (1)) + bufan "over."

The second element is itself a compound of be "by" (see by) + ufan "over/high" (from Proto-Germanic *ufan-, source also of Old Saxon, Old High German oban, German oben; from PIE root *upo "under," also "up from under," hence also "over").

From c. 1200 as "of higher rank or position, superior in authority or power; of higher rank than, superior to." This sense in Middle English perhaps was reinforced by a literal use of above in the sense "higher at the table than," thus "in a place of greater honor than, taking precedence over" (mid-14c.) From mid-14c. as "in addition to;" also "superior to, out of reach of, not condescending to." From late 14c. as "more" (in number, linear measurement, weight, value); "older; better than, more desirable than, superior to."

Phrase above all "before other considerations" is from late 14c. To be above (someone's) head in the figurative sense "out of range of his or her intellect" is from 1914 (above in the sense "not to be grasped or understood by" is from mid-14c.). In Middle English to be above erthe was "above ground, unburied," hence "living, among the living."