holy

This little adjective started life looking almost boring: something whole, sound, unbroken. Then Old English gave it a spiritual charge, so halig could mean not just “healthy” but set apart, untouchable, the way a crown jewel behind glass is untouchable. That’s why holy and health are cousins — same family, wildly different careers. By the Middle Ages, English speakers were even using it to translate Latin sanctus, and that’s the same world that later gave us sanctum, sanctuary, and sanctification. Put the pieces together and you get a word that began as “intact” and ended up meaning “so pure it belongs to God” — a pretty dramatic promotion for one old Germanic adjective.