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Etymology
From 🇰🇲.

Noun

 * 1) undercurrent wave, traditionally believed to be a sign of a storm.
 * 2)  swell: long and unbroken wave, or series of such waves
 * 3)  situation which appears to be calm but actually consists of secret or hidden movements or activities that may trigger a problem; person or group of persons carrying out such a movement or activity.