This study examines the complex structures of the largest etymological dictionary ever conceived, Walther von Wartburg's »Französisches Etymologisches Wörterbuch«. Employing metalexicographic methods the attempt is also made to characterise the way in which Wartburg's work reflects the specific nature of his linguistic scholarship. An extensive annexe investigates the 'covert structures' of the dictionary thus enhancing the user-value of the work.