The figurative meaning "acute or penetrating in intellect or perception" was in Old English; hence "keenly alive to one's own interests, quick to take advantage" (1690s). Of words or talk, "cutting, sarcastic," from early 13c. Meaning "distinct in contour" is from 1670s. The adverbial meaning "abruptly" is from 1836; that of "promptly" is first attested 1840. The musical meaning "half step above (a given tone)" is from 1570s. Meaning "stylish" is from 1944, hepster slang, from earlier general slang sense of "excellent" (1940). Phrase sharp as a tack first recorded 1912 (sharp as a needle has been around since Old English). Sharp-shinned attested from 1704 of persons, 1813 of hawks.
"having large, full eyes," 1620s, from ox + -eyed. An epithet used by Homer (boōpis) of the goddess Hera (Juno) and beautiful women. Oxeye has since c. 1400 been a name given to various flowering plants thought to resemble the eye of an ox; it is also used of certain birds, fishes, and a type of mirror.