I recently did a deep dive into Goetic etymology, chased the names through historical literature, primary sources, the works. Honest assessment? Most of them are Goetic natives with no traceable pre Christian origin. Only a handful stand out as legitimately older.
If you're in love with the mystical narrative around the Lemegeton's origins, the historical record will disappoint you. Sometimes it's better to just work with what's there rather than chase the backstory (read as: almost always)
That said, yes, I do believe the Jews deliberately demonized certain pagan deities and spirits. It was like a theological crowd control, a way to ensure no one burned offerings to competing entities, cause apparently thats bad. They weren't the first culture to do this and won't be the last.
To your actual question though; Vepar and Bitru have no historical evidence of anything predating the Book of Offices, which was Weyer's source for the Pseudomonarchia Daemonum, which fed into the Lemegeton. Goetic natives. And yet both are completely real to me. Whatever the historical story is, it doesn't change what shows up when you work with them.
Asteroth is one of the strongest cases of historical ties predating the Book of Offices. We just have to be careful about whats actually historical and accurate, and whats internet stuff that people think sounds cool. The latter being a cancer within the occult as a whole.
In my personal opinion, encountering a demon is incredible enough without the extras.
The messiness of the origins is just humans being human. It doesn't touch the reality of the contact.
