Etymology: Old English hálig , -eg (in inflection contracted to hálg- ), also Northumbrian hǽlig (whence northern Middle English hely ), Old Frisian hêlech , Old Saxon hêlag , -eg (Middle Dutch heilech , -egh- , Dutch heilig ), Old High German heilag (Middle High German heilec , German heilig ), Old Norse heilagr (Swedish helig , Danish hellig ) < Old Germanic type *hailag-oz , the sense of which is expressed in the Gothic of Ulfilas by weihs (but hailag , apparently ‘consecrated, dedicated’, is read on a Runic inscription generally held to be Gothic). A derivative of the adjective *hailo- , Old English hál , free from injury, whole, hale, or of the derivative noun *hailoz- , *hailiz- , in Old High German heil , Old Norse heill health, happiness, good luck, in Old Norse also omen, auspice: see -y suffix¹. The sense-development < hailo- is not clear, because the primitive pre-Christian meaning is uncertain, although it is with some probablity assumed to have been ‘inviolate, inviolable, that must be preserved whole or intact, that cannot be injured with impunity’, a sense preserved in Old Norse; hence the adjective would naturally be applied to the gods, and all things specially pertaining to them; and, with the introduction of Christianity, it would be a ready word to render Latin sanctus , sacer . But it might also start < hail- in the sense ‘health, good luck, well-being’, or be connected with the sense ‘good omen, auspice, augury’, as if ‘of good augury’: compare Old High German heilisôn , Old English hálsian , to halse v.¹, augur, divine, exorcise, etc. The sense arrangement here is therefore merely provisional; we cannot in Old English get behind Christian senses in which holy is equated with Latin sanctus, sacer.

Etymology: < holy adj., instead of the historical hallow v.¹