 It derives, ultimately, from the Proto-Indo-European verbal root "*ḱel-" ('to conceal, cover, protect'; compare with Latin "cēlō", Old Irish "ceilid", Greek "kalúptō").The Old Irish masculine noun "cel" ('dissolution, extinction, death') is also related.Other related early Germanic terms and concepts include the compounds "*halja-rūnō(n)" and *"halja-wītjan".'