The least heavy in weight, or having the least darkness (brightest); superlative form of 'light.'
From Old English 'leoht'; can mean either low weight (Germanic origin) or brightness (also Germanic); two different etymologies merged into one word.
The word 'light' is a linguistic accident where two totally different Old English words ended up spelled identically—one for brightness, one for weight—yet our brains somehow keep them separate.
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