No one outside of researchers knows what 0bola’s birth name was, or if it was ever changed legally. He has more than one AKAs. Barack Hussein Obama is definitely not a legal name; if his original name was ever legally changed to BHO there would have been a paper/legal trail.
If we believe what Obama has told us, his father was BHO Sr when he was born. Later he was legally adopted by Soetoro so his name was legally changed. So when was his name legally changed back to Obama?
Not that I believe any of that was ever true.