Shone brightly for a moment; displayed suddenly and briefly; moved very quickly like a flash of light.
From 'flash,' possibly from Middle English, imitating the sound or action of sudden bright light. May be related to Old Norse or Germanic origins, possibly onomatopoetic.
The word 'flash' itself might be onomatopoeia—it actually sounds like what it means, which is why children naturally understand it, and which is why it's been in use since the 1500s without much change in meaning.
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