Lexicography may seem to be nothing more than drudgery. However, there are many unexpected treasures waiting to reward the researcher. The context of 'pictura doctoricia' (instructive painting) in the 'translatio Severini' written in 902 by deacon John of Naples illustrates the authority of images and the function of iconography. The same theme recurs in the legend of the emperor Constantine and Pope Silvester, well-known throughout the Middle Ages. The recurrence of beautiful quotations from the homiliae in evangelia of saint Gregory the Great demonstrates how widely used this treatise was. Consideration of textual variants in excerpting can lead to the discovery of a new lemma, as in the case of exhereditas, and may highlight the transmission of rare words and the reception of texts.