Ghoul
Bram Stoker's 1897 novel Dracula has a character that acts much like a ghoul.  The character is named Renfield. Under the vampire's influence, Renfield becomes his willing slave. He develops a craving to eat living creatures in the hope of obtaining their life-force for himself. After being confined to an asylum, he considers eating a human hospital orderly, but finds he can only capture and consume flies, spiders, and the occasional bird.