The “Dictionnaire étymologique de l’ancien français” (DEAF) is a basic dictionary of Old French. It covers the period from 842 (Date of the Strasbourg vow of confederation between Ludwig the German and Charlemagne against Lothar I., handed down in Old High German and Old French) until the middle of the 14th century (period border to the Middle French, philologically and socially justified).
All available materials are evaluated: Dictionaries, glossaries, literary and non-literary texts. The slip box currently contains 1.5 million slips of paper, referring to some 12 million slips; it is supplemented by digital material. After the examination and interpretation of all references, all old French words with all their meanings are displayed from this mass and reduced to the article structure of the dictionary.
The DEAF is an etymological dictionary, which explains the origin of words and their development of meaning. To clarify the connections, the vocabulary is arranged according to families. The title word is the old French word, which developed directly from the etymon. The overall arrangement is alphabetical, so that the words of unknown origin can be placed in their alphabetically correct place. The description of etymology includes the neighbouring languages, the further life of the etymon in other Romance languages and, for example, the borrowings from Old French into English (example: gallop and galloping). Every meaning of a word is put into a definition. The contexts are generally taken from primary sources, i. e. they are not copied from dictionaries. This presupposes an indexing by the bibliography, which lists all texts, all manuscripts and all editions, classifies them in the history of belles-lettres and specialist literature, dates them, localizes them and critically assesses their quality.