A dictionary or glossary of a dialect or minority language, especially one dealing with a small area.
Origin
Early 19th century (in an earlier sense). From German Idioticon from post-classical Latin idioticon (from 1743 or earlier in work titles, as Idioticon Hamburgense, Idioticon Osnabrugense, Idioticon Prussicum) from ancient Greek ἰδιωτικόν, neuter singular of ἰδιωτικός.