gems, luster of gems, lustrous
璨 centers on the bright, shining quality of gems: their luster and sparkle. The meaning extends naturally to anything lustrous or gem-like.
璨 combines 王 (jade/gem) with 粲, which likely contributes the sound and the idea of brilliance or luster. The exact historical development of 粲 is uncertain, but the overall structure is a typical phono-semantic compound.
The left side 王 (jade) is a gem, and the right side 粲 looks like a sparkling, multi-part jewel. Picture a polished gemstone catching the light and shining brilliantly.
For サン, imagine the sun (サン) reflecting off a lustrous gem, making it sparkle: sun -> サン, and the gem's luster is as bright as sunlight.
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