Making quick, light, tapping sounds in rapid succession, like raindrops or small feet on a floor.
From Middle English 'pateren,' possibly imitative in origin, mimicking the sound itself. The 'patter' sound has been used since the 15th century to describe quick repetitive noises, and the -ing form creates the present participle.
The word 'patter' actually comes from the rapid recitation of prayers (Pater Noster), and over time people noticed that speedy prayer-saying sounded like quick tapping sounds, so the word evolved to mean any quick, light repetitive noise—how language captures onomatopoeia!
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