Meaning

noun the ratio of the volume occupied by packed red blood cells to the volume of the whole blood as measured by a hematocrit

noun a measuring instrument to determine (usually by centrifugation) the relative amounts of corpuscles and plasma in the blood

originFrom hemato- (“blood”) + Ancient Greek κριτής (kritḗs, “judge, umpire”), literally “to separate blood”, coined by Swedish physiologist Magnus Blix in 1891.

Etymology from Wiktionary, CC BY-SA 3.0