“Letter,” borrowed from Old French lettre, entered Middle English around AD 1200, eventually displacing the native English term bocstaf (i.e. bookstaff). Letter derives from Latin littera, which may have derived, via Etruscan, from the Greek “διφθέρα” (writing tablet).
The Middle English plural lettres could refer to an epistle or written document, reflecting the use of the Latin plural litteræ. Use of the singular letter to refer to a written document emerged in the 14th century.
