How does Abbe Busoni know Caderousse?

The Abbe (Dantes) had known Caderousse while he was a sailor. They were neighbors.

Yes, yes, Edmond, that is true, but you forgot at that time a little debt to our neighbor, Caderousse. He reminded me of it, telling me if I did not pay for you, he would be paid by M. Morrel; and so, you see, lest he might do you an injury——”