Makes soft murmuring sounds like a dove or pigeon, or expresses affection in a soft voice.
From Middle English 'coue,' imitative of the sound doves make. The word has Old French roots and is onomatopoetic, meaning it mimics the actual cooing sound. Over time it became associated with gentle, affectionate vocalizations.
The word 'coo' is one of the few English words that actually sounds like what it means—linguists call these 'onomatopoeia,' and they're found in every language. Interestingly, human babies begin cooing around 2-3 months old, the same gentle sounds doves make, suggesting we might be tapping into something deeply biological about expressing contentment.
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