Per 《左传·文公十八年》, 饕 means greed for wealth and 餮 greed for food. Tradition lists 饕餮 as one of the 四凶 ('Four Fiends') of Yao and Shun's age. Its bug-eyed mask, a symmetrical face with no body, stares out from the most famous Shang ritual bronzes.
memory
Both characters share the 食 ('eat') radical - a built-in clue that this beast is all about devouring.