I've known for years that "healthy," "hale," "whole" and "holy" come from the same root word. Of course, I'm not the only one.
This is from Carmen's Blog.
“Holy,” “Whole,” “Healthy,” and “Hale”
"Tonight I watched the movie, A Man for All Seasons, and it made me wonder about the etymology of 'oath.' I looked it up. I thought you’d like to see this.
"The word 'oath' comes from the Old English word, 'áð.' They even look similar. The only difference is in OE it sounded like 'ah' at the beginning and of course now 'oh.' So 'oath' is kind of like the word, 'God,' which comes from the Old English word, 'God.' You go back so far, and unless you’re going to go back to the Indo-European educated guesses, you have to stop pretty much with Old English, so they are like really old, really mysterious words, unlike (to my mind) the word 'enthusiasm,' where you can say, 'And this word breaks up into ‘the God within.’'
"But here’s the really interesting point. 'To take an oath,' or 'to swear' in Old English is 'gehalsian.' That literally means 'to make holy.' This is interesting because 'Savior' or 'Christ' in OE is 'Hǽlend.' That literally is 'Healer.' 'Holy' is 'halig' in Old English. 'Healing' is 'hǽling.' 'Health' or 'salvation' is 'hǽlþ.' 'To heal' is 'hǽlan.' You say 'Hello' by saying 'May you be hale' or 'Wes þu hal.' So 'hale' or 'whole' is 'hal' in OE. All this to say that the root for Savior, Christ, holy, healthy, salvation, healing, whole, hale, and swear/to make holy are all the same–'hal' or 'hǽl,' which are really the same in Old English, just variants of the same root. So all of these words come from 'hal,' for 'whole,' 'holy,' and 'to heal.' So Savior, Christ, holy, healthy, salvation, healing, whole, hale, and swear/to make holy all mean pretty much the same thing, to an Anglo-Saxon. 'Whole.' You think of 'integrity.' Is that not absolutely awesome?! It’s like a poem, only it’s etymology."