What's the "een" in Halloween?
1847, from cardio- + -logy. Cardiologist attested from 1885.
cardiology car·di·ol·o·gy (kär'dē-ŏl'ə-jē)n. The medical study of the structure, function, and disorders of the heart.
The branch of medicine devoted to the study and care of the heart and circulatory system.