Origin: ModL, orig. neut. of L caesius, bluish-gray (< IE base *(s)kai-, bright > -hood): so named (1860) by Robert Wilhelm Bunsen because of the blue line seen in the spectroscope
See cesium in American Heritage Dictionary 4
also cae·si·umnoun Symbol Cs
Origin: From Latin caesius, bluish gray (from its blue spectral lines).
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