Etymologically, “debit” comes from the Latin debitum, meaning “something owed.”  “Credit” comes from creditum, meaning “something entrusted” (from credere “to trust, to believe”).

Well, that was pretty straightforward.

P.S. Saying “PIN number” is redundant (personal identification number number).  I hope the guy I always see at Quiktrip reads this.  I should probably translate this post into Urdu.