Making a high, clear sound by blowing air through pursed lips, or a similar sound made by wind or steam.
Old English 'hwistlian' is imitative in origin—it mimics the actual sound. Germanic languages share similar forms, all copying the noise itself.
Whistling appears in languages worldwide because it's one of the few human sounds that's purely imitative—'whistle,' 'pfeifen' (German), and 'siffler' (French) all started from people actually making the sound and naming it.
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