letter: [13] The distant ancestry of the word letter has never been satisfactorily explained. One possible candidate as a source that has been put forward is Greek diphthérai ‘writing tablets’. But the earliest precursor that can be positively identified is Latin littera. This meant ‘alphabetic symbol’, or in the plural ‘document’ and ‘epistle’. English acquired it via Old French lettre. Also from Latin littera are English literature and obliterate [16], which means etymologically ‘remove letters’. => literature, obliterate[letter etymology, letter origin, 英语词源]