Never been tested, tried, or proven; not yet examined to see if something works.
From Old English 'un-' (not) plus 'tested' (from Latin 'testari' meaning to witness or prove). The prefix was productively applied to create the opposite meaning.
The prefix 'un-' is so powerful in English that you can slap it on almost any adjective to flip its meaning—'tested' becomes 'untested,' 'happy' becomes 'unhappy'—it's the ultimate linguistic shortcut!
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