@sujato
Well the same thing happens with words like "Dharma’ and ‘karma’ which are often left untranslated (and the Sanskrit words used even when talking about EBTs) since they’ve become part of the English language it seems these days (though I assume you’re translating them?) I’m not sure how much you can ‘control’ with a single word translation how people tend to understand things in terms of their pre-existing views… obviously good to try and minimize this tendency when possible, but context is also important for understanding.
Also maybe occasionally using Pali terms will help people who read the suttas see how the Buddha often used exisiting terms but redefined them. And start thinking accordingly… Some technical terms in Pali simply just cannot be adequately translated in English… I think sometimes attempting to limits their meaning too much and actually feeds into people (mis)understanding the meaning based on their pre-exitsing views instead of encouraging people to think in terms of context (as well as the interrelationship betwen the various teachings). The problem is compounded due to the various connotations the word might carry in English which the original Pali doesn’t (one of the problems of course with ‘concentration’).
Maybe you should add ‘unification (of mind)’ to the list and let people vote for a second choice Also I do like what @Brahmali mentioned somewhere about the value of the emotional quality the word evokes (and although I think ‘stillness’ is too generic, ‘unification’ or many of the other choices don’t rate high for me in this regard). Sometimes the Pali can do this more. It’s why I don’t care much for chanting translated into English (and I felt this way before I even knew any Pali at all).
BTW, speaking of such things, how did you decide to translate ‘metta’? I think that’s really another candidate for leaving in Pali (and often is).