Completely without wind or breeze; calm and still in the air.
From 'breeze' (possibly from Portuguese 'brisa' or Spanish 'brisa', imported to English in the 17th century) plus the negation suffix '-less' (Old English 'leas'). The term is relatively modern in English.
Sailors historically feared breezeless days more than storms—being becalmed meant your ship could drift toward rocks or pirates with no power to escape, making stillness dangerous rather than peaceful.
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