Refrain is a fascinating word.
Taken as a noun, it is a technical musical term referring to that melody to which you always return. In literary terms, it is the familiar, sometimes nagging phrase from your lecturing dad, or needy spouse. It’s a return, something you come back to. Taken as a verb, however, to refrain is to keep from – to avoid. It carries the suggestion that you might have done something, but managed to avoid it. I think of skateboarding in front of the library, smoking in the bar, et cetera.
The etymology of the two instances goes back the same amount of time – the 14th century – but one’s Latin root comes from “frenum”, to bridle, as a horse. The other, from “refringere”, from “frangere”, to break.
Not much to report here: A refrain is something which you always come back. To refrain is something which you must keep from living in the same word strikes me. Opposites, living in the same word.