The Modern English word devil derives from the Middle English devel, from the Old English dēofol, that in turn represents an early Germanic borrowing of the Latin diabolus. This in turn was borrowed from the Greek: διάβολος diábolos, "slanderer".
The word satan comes from the Hebrew language as the English word "adversary". According to Peter H. Gilmore, "The Church of Satan has chosen Satan as its primary symbol because in Hebrew it means adversary, opposer, one to accuse or question. | This is based to LaVeyan Satanists
Satan is the name of the one we worship. The word devil is an epithet bonded throughout history with Satan.
Extra:
The word demon comes from the Greek word "daimon" or else knowledge. Also means divine creature.