late 14c., "blood-red, of a blood-red color" (late 12c. as a surname), from Old French sanguin (fem. sanguine) and directly from Latin sanguineus "of blood," also "bloody, bloodthirsty," from sanguis (genitive sanguinis) "blood" (see sanguinary).
The meaning "cheerful, hopeful, vivacious, confident" is attested by c. 1500, because these qualities were thought in old medicine to spring from an excess or predominance of blood as one of the four humors. The sense of "of or pertaining to blood" (mid-15c.) is rare.
Also in Middle English as a noun, a type of red cloth (early 14c.). It sometimes was used in the senses now going with sanguinary.
"state of being disordered or ruffled," hence "agitation, perturbation," 1813 (carfuffle), first attested in Scottish writers, from a verb meaning "to disorder, dishevel" (1580s), of obscure origin, probably from a dialect word based on Scottish verb fuffle "to throw into disorder" (1530s). The first element is perhaps as in kersplash, etc. (see ker-); OED points rather to a Gaelic car "twist, bend, turn about".
also coldblooded; 1590s, of persons, "without emotion, wanting usual sympathies, unfeeling;" of actions, from 1828. The phrase refers to the notion in old medicine that blood temperature rose with excitement. In the literal sense, of reptiles, etc., "having blood very little different in temperature from the surrounding environment," from c. 1600. From cold (adj.) + blood (n.). Related: Cold-bloodedly; cold-bloodedness.