The word sanguine means "optimistic" and the word sanguinary means "involving a lot of bloodshed". How could these possibly be related? It traces to the idea of bodily humors - in the olden days, people believed that an excess of blood resulted in a cheery disposition. Going further back, both words were borrowed at some point during the fourteenth century from the Latin noun sanguinarius, meaning "of or pertaining to blood". Through Proto-Italic, that ultimately derives from the Proto-Indo-European reconstruction kreue, which referred to blood outside the body (the PIE speakers distinguished between whether it was on the interior or exterior). In heraldry, the word sanguine can also refer to a type of blood-red tincture used in flags like Latvia's.
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.