Sky is Norse, from Old Norse sky, borrowed in the mid-1200s, and the hard sk- gives it away. The remarkable thing is what it originally meant: a cloud. The word comes from a Germanic root meaning "cloud cover," from an older root meaning "to cover, conceal," and its relatives are all about shade and covering — Old Norse skuggi, "shadow," Gothic skuggwa, "mirror."
Old English had its own descendant of the same root, sceo, and its own word for the heavens, heofon. Sky took over the sense of the upper air by about 1300, pushing heaven up into the religious register where it now lives. In Middle English sky could still mean both cloud and heaven at once, and the older sense survives in the plural: the skies originally meant the clouds.
sky (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). also from mid-13c. sky (v.) "to raise or throw toward the skies," 1802, from sky (n.). By 1865 in reference to paintings hung near the ceiling in an exhibit. Related: Skyed ; skyer ; skying . also from 1802
sky came in through Old Norse, and its spelling follows that family's conventions.
How that family writes these sounds
| /sk/ at the start | sk-, never sc- or sh-sky, skin, skirt, skull |
What gives it away on the page
| sk- | Native sc- had already softened to sh-, so a hard sk- came from somewhere else.sky, skin, skirt, skill, skull |
Placing it without the spelling
| blunt everyday things — and a few words too basic to look borrowed | Old Norsesky, knife, window, law |
| a hard /sk/ at the start | Old Norsesky, skin, skirt, skull |
Old Norse in the spelling guide · guess another word's family