Gabriel is a conjunction of gabri- (heroic man), and -el (god), roughly translating to "man of God". -el is just a generic proto-semitic word for god that long predates any sort of written language. gabri- is likely related to a well known Aramean king named Gabbār, documented in the Kilamuwa stela alongside his (honorable) god Ba'al SMD. It's entirely possible that there's some recursive etymology here though, as is common with dynastic names.