Original: The term adrenaline is derived from the Latin roots ad - and renes and literally means "on the kidney", in reference to the adrenal gland's anatomic location on the kidney. The Greek roots epi and nephros have similar meanings, and give rise to "epinephrine".
Simplified: The Latin roots ad - + renes and the Greek roots epi - + nephros both mean into\/onto the kidney, which is a reference to the adrenal glands.