'Ruby' is Latin for 'red' — from 'rubeus.' It shares its PIE root with 'red,' 'rust,' and 'rouge.'
A precious gemstone consisting of the mineral corundum (aluminum oxide) in a deep red color, caused by trace amounts of chromium.
From Middle English 'rubi,' from Old French 'rubi,' from Medieval Latin 'rubīnus (lapis)' (red stone), from Latin 'rubeus' (red, reddish), from 'rubēre' (to be red), from PIE *h₁rewdʰ- (red). This PIE root is the ancestor of the 'red' color words across most Indo-European languages: English 'red' (via Proto-Germanic *raudaz), 'rust' (the red corrosion), 'rouge' (French, from Latin 'rubeus' via 'russus'), 'rubric' (originally a heading written in red ink), 'robust' (from Latin 'robustus,' from 'rōbur' — red oak, hence strength), and 'corroborate' (to strengthen together). Sanskrit 'rudhirá' (red, bloody), Greek
'Ruby' and 'red' are distant cousins from the same PIE root *h₁rewdʰ-. So are 'rouge,' 'rubric' (originally written in red ink), 'rubella' (red rash disease), 'robust' (originally 'oaken, strong' from Latin 'robur,' from the red wood of the oak), and 'rust' (the red oxidation). The color red has generated a vast family