Touching with the lips as a sign of affection, greeting, or romantic interest.
From Old English 'cyssan,' likely imitative in origin (representing the sound of a kiss). The word has remained relatively unchanged for over a thousand years because the action is so ancient.
The word 'kiss' is probably imitative—it sounds like the action itself, which is why it sounds similar across many languages (German 'küssen,' Swedish 'kyssa')—we literally copied the sound humans make into a word.
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