Usually I start wondering about a word’s etymology after encountering the word somewhere — today, though, it was not seeing the word that got me cogitating.
A poster on a message board was grousing about people who can’t restrain themselves from doing [whatever]. My always-active editor mind automatically wanted to change that to refrain from doing [whatever] — one fewer word, and it avoids the clunky reflexive pronoun. Restrain, refrain, weird that those two words are so close — and hey, what’s the connection between the verb refrain and its apparently identical noun twin?
As we found with sconce/ensconce, despite the surface similarity, the two words have different etymological roots.
According to the Online Etymology Dictionary, the verb refrain, meaning to hold oneself back from doing something, dates back to the early 14th century. It comes (via Old French) from the Latin refrenare “bridle, hold in with a bit,” from re– “back” + frenare “restrain, furnish with a bridle,” from frenum “a bridle.”
Frenum, by the way, hasn’t disappeared without a trace — the strip of tissue between your tongue and the floor of your mouth is the lingual frenulum, with frenulum being the diminutive of frenum. (And, to further digress, the original meaning of “tongue-tied” is to have an abnormally short lingual frenulum.)
The noun refrain, meaning a recurring part of a song or poem, especially one that appears between verses, dates to the late 14th century — though, per the Online Etymology Dictionary, it’s uncommon until the 19th century. Like the verb, it comes from the Latin via the French, but both the route and the root are different. It comes from the Provençal refranhar “singing of birds, refrain,” which comes from the Vulgar Latin refrangere “break off.” As OED says, “The notion is of something that causes a song to ‘break off’ then resume.” This sense of “refrain” may be the source of “riff,” a recurring phrase in jazz.