Calypso

Proto-Indo-European root meaning "to cover, conceal, save."

It forms all or part of: Anselm; apocalypse; Brussels; caliology; Calypso; calyx; ceiling; cell; cellar; cellular; cellulite; cellulitis; cilia; clandestine; cojones; coleoptera; color; conceal; eucalyptus; hall; hell; helm (n.2) "a helmet;" helmet; hold (n.2) "space in a ship below the lower deck;" hole; hollow; holster; housing (n.2) "ornamental covering;" hull (n.1) "seed covering;" kil-; kleptomania; occult; rathskeller; supercilious; Valhalla; William.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit cala "hut, house, hall;" Greek kalia "hut, nest," kalyptein "to cover," koleon, koleos "sheath," kelyphos "shell, husk;" Latin cella "small room, store room, hut," celare "to hide, conceal," clam "secret," clepere "to steal, listen secretly to;" Old Irish cuile "cellar," celim "hide," Middle Irish cul "defense, shelter;" Gothic hulistr "covering," Old English heolstor "lurking-hole, cave, covering," Gothic huljan "to cover over," hulundi "hole," hilms "helmet," halja "hell," Old English hol "cave," holu "husk, pod;" Old Prussian au-klipts "hidden;" Old Church Slavonic poklopu "cover, wrapping."

also Hell, Old English hel, helle, "nether world, abode of the dead, infernal regions, place of torment for the wicked after death," from Proto-Germanic *haljō "the underworld" (source also of Old Frisian helle, Old Saxon hellia, Dutch hel, Old Norse hel, German Hölle, Gothic halja "hell"). Literally "concealed place" (compare Old Norse hellir "cave, cavern"), from PIE root *kel- (1) "to cover, conceal, save."

Old Norse Hel (from Proto-Germanic *halija "one who covers up or hides something")was the name of Loki's daughter who ruled over the evil dead in Niflheim, the lowest of all worlds (nifl "mist") It might have reinforced the English word "as a transfer of a pagan concept to Christian theology and its vocabulary" [Barnhart].

In Middle English, also of the Limbus Patrum, place where the Patriarchs, Prophets, etc. awaited the Atonement. Used in the KJV for Old Testament Hebrew Sheol and New Testament Greek Hades, Gehenna. Used figuratively for "state of misery, any bad experience" at least since late 14c. As an expression of disgust, etc., first recorded 1670s.

To have hell break loose is from c. 1600. Expression hell in a handbasket is attested by 1867, in a context implying use from a few years before, and the notion of going to Heaven in a handbasket is from 1853, implying "easy passage" to the destination. Hell or high water (1874) apparently is a variation of between the devil and the deep blue sea. To wish someone would go to hell is in Shakespeare ("Merchant of Venice"). Snowball's chance in hell "no chance" is from 1931; till hell freezes over "never" is from 1832.

To do something  for the hell of it "just for fun" is from 1921. To ride hell for leather is from 1889, originally with reference to riding on horseback. Hell on wheels is from 1843 as the name of a steamboat; its general popularity dates from 1869 in reference to the temporary workers' vice-ridden towns along the U.S. transcontinental railroad. Scottish had hell-wain (1580s) "a phantom wagon seen in the sky at night."