Answer: At arm's/arms' length

[mendax.livejournal.com]

starwatcher307 would like to know whether you keep something "at arm's length" or "at arms' length."
With examples from Leverage.



This idiomatic expression is most often used figuratively, to express a deliberate lack of intimacy or personal closeness.

Sophie was so good at emotional connections — confidante, accomplice, den-mother to them all — that it was easy to forget how much she kept them at arm's length, how little they really knew about her.

I remember, when I was a wee thing, not understanding the proverb "A stitch in time saves nine." Saves nine what? Or whom? I didn't understand the idiom because I was unfamiliar with what it means literally — that if you sew up a hole in fabric right away, it won't tear further. (It's a shame, because the lesson that getting something done promptly can save you more work later on is one that I, as a master procrastinator, would have done well to internalize at a young age.)

Anyway, personal digressions aside, if we go from the figurative meaning of "at arm's length" to the literal meaning, it's easier to see where the apostrophe should go. Something kept at arm's length physically would be held away from you by the length of one arm. And we know that the singular possessive form puts the apostrophe before the ess. That placement doesn't change when the expression is used figuratively. (Or, for that matter, with a tongue-in-cheek literal use.)

Eliot held the bodyguard at arm's length (also six inches off the floor) with one hand clenched around his throat.

I find that visualizing this expression, picturing someone literally holding something away at one arm's length, helps me remember that the apostrophe should go before the ess. And if the someone I'm visualizing happens to be Eliot Spencer? Hey, all the better for me.