The story
From poly- + -cyte + -emia, with /θ/ for euphony; akin to poly- + -cyte + hem- + -ia; morphologically parallel with erythrocythemia.
Etymology from Wiktionary, CC BY-SA 4.0.
polycythemia
Today it means: A rare disorder in which the bone marrow produces an abnormally large amount of blood cells, often red blood cells. Full definition →