In reply to Michael Gordon:
Thanks Michael, I'm probably not with the kids on this one- it being a term I've never been taught on a course, or employed in 'real life'. I'm also not sure it means something else entirely different from Take In, but there you go.
Perhaps that's the real problem. My immediate thoughts are that the 'communication system' has too many terms in it. What you might gain in 'subtlety' by being able to employ lots of different terms, you lose in overall degraded communication.
Why not say the traditional "Watch me"? This tells a belayer to be alert that he's about to take a climbers load. It has more similar phonetics to "Take in", and would have non-lethal implications if misunderstood. Okay, there's a subtle difference, but a non lethal one, and actually not a difference that makes any real difference to what's needs to be done.
The military have a limited number of phrases used in 'contact drills'. Here communication needs to be quickly understood, and probably over the noise of gunfire, etc. A bit like climbing where we might have to should over the sound of wind, etc. The number of phrases is relatively limited, and also follow a phonetic pattern so that 'Break Left' won't be misunderstood from 'Magazine', "Man Down" or 'Rally Rally Rally' in a particular context.
The other aspect to these limited number of terms is that they 'embed' as a kind of automatic response that doesn't require conscious thought. The more terms you have, the more subtlety you can employ, the more the listener has to think about what's going on.
Exactly the same principle was given to me when I learnt to climb. A much more limited number of 'calls' was taught, and each is unlikely to be misunderstood 'lethally'- hence 'Slack' vs 'Take in' are good and distinct. 'Safe' vs 'Off Belay' can't be misunderstood, etc. So, when a partner is climbing you'll either hear 'Slack', 'Take in', 'Watch me' or 'Saaaafe'. I can't think of an additional term that would make climbing safer- I'm sure someone will argue that, but I'll leave that to them to convince me.
The point is that this limited number of terms is unlikely to be misunderstood. Even if the actual letters can't be made out, say if the wind is blowing, then the 'tempo' of the sounds makes them relatively comprehensible.
A proliferation of terms (some of which I'm not convinced the world really needs, such as 'Take') will tend to make each less likely to be easily understood, and also less quickly reacted to. Overall, communication is degraded, and more likely to be 'lethal'.