What is the X in X-mas?
1833, from comb. form of root of cyanosis + -ic.
"blue disease," the "blue jaundice" of the ancients, 1820, Medical Latin, from Greek kyanosis, from kyanos "dark blue color" (see cyan) + -osis.
cyanosis cy·a·no·sis (sī'ə-nō'sĭs)n. A bluish discoloration of the skin and mucous membranes resulting from inadequate oxygenation of the blood.