Thanks! Are they always used interchangeably? Is nebo more popular than anebo?
"Anebo" is typically used when the options are exclusive, either one or another. Like in this sentence.
In situations where you have a list of options but they are not exclusive (you can get a chocolate or strawberry ice-cream from the stall - meaning they have both available and you could get both if you wanted), "nebo" is better. Nebo is fine in both situations.
It did start as a + nebo. And you may sometimes find people pronouncing it like two words.