epistle (n.) Look up epistle at Dictionary.com
partly from Old English epistol and in part directly from Old French epistle, epistre (Modern French épitre), from Latin epistola "a letter," from Greek epistole "message, letter, command, commission," whether verbal or in writing, from epistellein "send to, send as a message or letter," from epi "to" (see epi-) + stellein in its secondary sense of "to dispatch, send" from PIE *stel-yo-, suffixed form of root *stel- "to put, stand," with derivatives referring to a standing object or place (see stall (n.1)). Also acquired in Old English directly from Latin as pistol. Specific sense of "letter from an apostle forming part of canonical scripture" is c.1200.