Old English scearp "having a cutting edge; pointed; intellectually acute, active, shrewd; keen (of senses); severe; biting, bitter (of tastes)," from Proto-Germanic *skarpaz, literally "cutting" (source also of Old Saxon scarp, Old Norse skarpr, Old Frisian skerp, Dutch scherp, German scharf "sharp"), from PIE root *sker- (1) "to cut" (source also of Lettish skarbs "sharp," Middle Irish cerb "cutting").
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 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.
c. 1200, doublen, "to make double; increase, enlarge, or extend by adding an equal portion, measure, or value to," from Old French dobler, from Latin duplare, from duplus "twofold, twice as much" (see double (adj.)). Intransitive sense of "to become twice as great" is from late 14c.
From mid-14c. as "to duplicate;" from late 14c. as "to repeat, do twice;" from c. 1400 in the transitive sense of "lay or fold one part of upon another." By 1540s as "to pass round or by." Sense of "turn in the opposite direction" is from 1590s. Meaning "to bend or fold" (a part of the body) is from early 15c.; to double up bodily is from 1814.
A blow on the stomach "doubles up" the boxer, and occasions that gasping and crowing which sufficiently indicate the cause of the injury .... [Donald Walker, "Defensive Exercises," 1840]
Meaning "to work as, in addition to one's regular job" is c. 1920, circus slang, from performers who also played in the band. Related: Doubled; doubling.
1836, "abruptly" from sharp (adj.). The sense of "promptly" is attested by 1840.
"a cheat at games," 1797, short for sharper (1680s) in this sense. Meaning "an expert, a connoisseur" is attested from 1840, and likely is from sharp (adj.). Musical sense of "a tone a half-step above a given tone" is from 1590s; as the name of the character which denotes this, by 1650s. The noun was used 14c. as "a pointed weapon, edge of a sword" and sharps is by 1834 as the name of one of the three usual grades of sewing needles (with blunts and betweens).
late 14c., "an amount twice as great, a twofold quantity or size," from double (adj.). From mid-15c. as "a duplicate copy, something precisely like another."
Sense of "a backward turn to escape pursuers" is from 1590s. Stage sense of "performer or singer fitted to supply the place of a principal in an emergency" is by 1800, originally in opera. The Hollywood stunt double is by 1945. Meaning "an alcoholic drink with twice as much liquor as usual" is by 1922 (double drink is from 1901). Tennis sense of "game played by two on each side" is by 1884. Baseball sense of "a hit in which the batter safely reaches second base" is by 1938. In betting, double or nothing is by 1899 (double or quit is from 1570s).
c. 1300, "twice as much or as large," also "repeated, occurring twice," also "of extra weight, thickness, size, or strength; of two layers," from Old French doble (10c.) "double, two-fold; two-faced, deceitful," from Latin duplus "twofold, twice as much," from duo "two" (from PIE root *dwo- "two") + -plus "more" (see -plus).
From early 14c. as "having a twofold character or relation," also "consisting of two in a set together; being a pair, coupled." From mid-14c. as "characterized by duplicity." The earliest recorded use in English is c. 1200, in double-feast "important Church festival."
Double-chinned is from late 14c.; double-jointed, of persons, is by 1828. Military double time (1833) originally was 130 steps per minute; double quick (adj.) "very quick, hurried" (1822) originally was military, "performed at double time."
The photographic double exposure is by 1872. The cinematic double feature is by 1916. Double figures "numbers that must be represented numerically by two figures" is by 1833. Double-vision is by 1714. Double indemnity in insurance is by 1832; double jeopardy is by 1817. The baseball double play is by 1866.
Double trouble "twice the trouble" is by 1520s; in 19c. America it was the name of a characteristic step of a rustic dance or breakdown, derived from slave dancing on plantations. A double-dip (n.) originally was an ice-cream cone made with two scoops (1936); the figurative sense is by 1940. Double bed "bed made to sleep two persons" is by 1779. Double life "a sustaining of two different characters in life" (typically one virtuous or respectable, the other not) is by 1888.
"twice, doubly," late 14c., from double (adj.). Double-dyed "twice dyed, deeply imbued," but usually figurative, "thorough, complete" is from 1660s. To see double "by illusion to see two images of the same object" is from 1650s.
To double check "check twice" is by 1958 (see check (v.1)). Related: Double-checked; double-checking. To double-space (v.) in typing is by 1905. Related: Double-spaced. To double book in reservations is by 1966. To double park "park (a vehicle) parallel to another on the side toward the street" is by 1917. Related: Double-parked; double-parking.