mathema, good one.
Debit is existing (if only virtually) where as credit is an existing amount in action, so a variable of whether the amount will change, it could cancel, or not go through for some reason. Therefor credited until the exchange, and I believe taken out at the end of each statement month or period. As different from Debit because that comes off the bank total that day.
HUH.. although this website says Debit is derived from debitum, meaning something owed. Or Debt......OH, I get it it is deb-ted because the bank owes it to you. I love words. Credited because you owe the bank.