skyhook n.

mid-13c. (c. 1200 as a surname), skie, sci, skei, "a cloud," from Old Norse sky "cloud," from Proto-Germanic *skeujam "cloud, cloud cover" (source also of Old English sceo (Middle English sceu) "the sky, the heavens," Old Saxon scio "cloud, region of the clouds, sky;" Old High German scuwo, Old English scua, Old Norse skuggi "shadow;" Gothic skuggwa "mirror"), from PIE root *(s)keu- "to cover, conceal."

The meaning "upper regions of the air; region of clouds, wind, and rain; the heavens, the firmament" is attested from c. 1300; it replaced native heofon in this sense (see heaven). In Middle English, the word can still mean both "cloud" and "heaven," as still in the skies (c. 1300), originally "the clouds."

Sky-high "as high as the sky" is from 1812; optimistic phrase the sky's the limit is attested from 1908. Sky-writing is from 1922. Sky-diving "sport or activity of jumping from an aircraft and free-falling before landing by parachute" is attested from 1959 (sky-diver by 1961; sky-dive (v.) by 1965).

"bent or angled piece of metal or other substance used to catch or hold something," Old English hoc "hook, angle," perhaps related to Old English haca "bolt," from Proto-Germanic *hokaz/*hakan (source also of Old Frisian hok, Middle Dutch hoek "a hook;" Dutch haak "a hook, angle, corner, cape," German Haken "hook"), from PIE root *keg- "hook, tooth." For spelling, see hood (n.1).

Also the name of a fireman's tool for tearing into buildings, hence hook-and-ladder (1821). Meaning "holder for a telephone receiver" is from 1885 and continued in use after the mechanism evolved. Boxing sense of "short, swinging blow with the elbow bent" is from 1898. Figurative sense "that which catches, a snare, trap" is from early 15c. Meaning "projecting point of land" is from 1670s; in U.S. use probably reinforced by the Dutch word.

This name is given in New York to several angular points in the North and East rivers; as Corlear's Hook, Sandy Hook, Powles's Hook. [Bartlett, "Dictionary of Americanisms," 1848]

Off the hooks meant "disordered" (16c.), "unhinged" (1610s) and "dead" (1840). By hook or by crook (late 14c.) probably alludes to tools of professional thieves. Hook, line, and sinker "completely" is 1838, a metaphor from angling. Hook-nose (n.) is from 1680s; hook-nosed (adj.) from 1510s. Hook-and-eye as a method of garment fastening is from 1620s.

Hook and eye, a metallic fastening for garments, consisting of a hook, commonly of flattened wire bent to the required shape, and an eye, usually of the same material, into which the hook fits. Under the name of crochet and loop, this form of fastening was in use as early as the fourteenth century. [Century Dictionary]