kayl-
“whole, uninjured, holy”holy/whole
PIE root meaning whole, uninjured, or holy. Source of English "whole," "health," "holy," and words linking wholeness to sanctity.
Discussion
*kayl- is a Proto-Indo-European root meaning "whole," "uninjured," or "holy," linking physical wholeness to spiritual holiness—a conceptual connection preserved across multiple branches.
The root gives Old English hāl "whole, healthy" (modern English whole, hale) and hāliġ "holy" (modern English holy). The semantic development from "whole/intact" to "sacred" reflects the PIE association between completeness and divine perfection. German heil "salvation, health" and heilig "holy" continue both senses.
Old English hǣlþ "health" (modern English health) and hǣlan "to heal" (modern English heal) derive from the same root—to heal is to make whole again. The greeting "hail" and the proper name Helga ("holy one") are further reflexes.
In other branches, Old Church Slavonic cělŭ "whole" and Welsh coel "omen" (from wholeness as a sign of divine favor) extend the attestation. Greek koîlu is sometimes connected but this is disputed.
The conceptual chain whole → healthy → holy is preserved intact in English, making this root one of the most semantically transparent survivals from PIE. Modern descendants include whole, holy, hale, heal, health, hail, and halcyon (disputed).
Notes
Source of English "holy", "whole", "hale". Germanic *hailaz (whole/sacred).