Wherefore art thou, aberil?

[Mauro]

For what it's worth, I think the difficult part in deriving 'Aberil' from 'Aprilis' is the change p->b, rather than the intervening 'e' (we have seen various examples in various languages of an 'e' inserted between a consonant and 'r'). If this is true, Portuguese 'Abril' should be the modern form nearest to 'Aberil'.