Of course, the reason 'sanguine' means cheerful or optimistic goes back to Plato's humoral theory of personality. Plato believed our personalities are dominated by one of four 'humors' (i.e., bodily fluids); blood, black bile, yellow bile or phlegm. Those dominated by blood were cheerful and optimistic. Similarly, we still have the word 'phlegmatic' as a personality descriptor.

And then there are people like JK Rowling who name the vampires "Sanguini" and give them a gloomy personality. :o)

Welcome
rkeefer and trident; hope you enjoy your stay.
When I was a boy, the local TV station had an after-school
special wherein the 'fright' show being broadcast was
introduced by a charachter called "Dr. Sanguinary".
He was anything but cheerful.

Sanguine is also a natural mineral (chalk) from which crayons are made.
Leonardo da Vinci made beautiful sanguines. wiki sanguine drawing

O, yes, I had forgotten that, but I remember the picture. Thanks.