Hieronymus, pronounced /haɪˈrɒnɪməs/, is the Latin form of the Greek male given name Ἱερώνυμος (Hierṓnumos), literally meaning "sacred name" (from hieros, meaing 'holy' and onyma, meaning 'name'). It has entered modern English as Jerome, or, even more informally, Jerry.
While the most famous man to bear this name was probably Saint Jerome (originally Eusebius Sophronius Hieronymus), the man who, among other things, first translated the Bible into Latin, he was certainly not the first to use the name. It has a long and bloody past among the Greek. Perhaps the first person of note to be named Hieronymus was Hieronymus of Cardia, a Greek general and historian who lived from 356 BCE to 323 BCE. Of course, today more people are likely to recognize more modern celebrities, and the Dutch artist Hieronymus Bosch is the first Hieronymus to come to most people's mind.
Although Hieronymus translates into Geronimo in Italian (and more relavantly, Jerónimo in Spanish), the most famous American Geronimo was actually named with a good old-fashioned Mescalero-Chiricahua name: Goyaałé, meaning 'one who yawns'; the Mexicans, not knowing what make of this, figured that Geronimo was close enough.
These days you are most likely to find the name Hieronymus as a character in a children's/YA book, either as an evil villain, an odd old man, or an old-timey adventurer. The popularity of this name in literature was no doubt helped along by the Baron Karl Friedrich Hieronymus von Münchhausen (1720-1797), a German adventurer with a tendency to exaggerate. His adventures were recounted in the 1785 novel The Surprising Adventures of Baron Munchausen by Rudolph Erich Raspe.