Dr. W. Graham Scroggie said, in one of his addresses, as he asked his audience to turn to Paul's Letter to the Romans, that he preferred the simple word 'letter' to the word 'epistle' to describe the didactic writings of Paul, Peter, James, John and Jude in the New Testament. Every child, he said, knew what a letter was, but there were many like the child in Sunday School who, when asked what an epistle was, replied that it meant the wife of an apostle.
In olden times they had a kind of manuscript called 'Palimpsest', and on it bad things, mischievous things and plays, as well as dirty, obscene stories, were written. At that time skins were scarce and people often used those skins for recording portions of Scripture. They rubbed off the bad writing and wrote on them portions of the Gospel. What a different message the skins then conveyed!
(2 Cor. 3. 2, 3)