Meaning

noun a specially long, formal letter

noun a book of the New Testament written in the form of a letter from an Apostle

originPIE word *h₁epi The noun is derived from Middle English epistel, epistole, pistel (“letter; literary work in letter form; written legend or story; spoken communication; (Christianity) one of the letters by an apostle in the New Testament; extract from such a letter read as part of the Mass”) [and other forms], and then partly: * from Old English epistol, epistola, pistol (“letter, epistle”), from…

Etymology from Wiktionary, CC BY-SA 3.0