The patron devil of calligraphy, Titivillus (alternately Tytyvyllus) is cited occasionally in various manuscripts as the reason for errors and omissions in texts copied by pious scriptorial monks. The earliest know mention of Titivillus appeared c. 1285 in John of Wales Tractatus de Penitentia - "Fragmina psalmorum / Titivillus colligit horum" (loosely: Titivillus collects bits of the psalms).

Titivillus preyed on "Janglers, cum jappers, nappers, galpers, quoque drawers, momlers, forskippers, overenners, sic overhippers ..." 1 that is: those that talk fast or jestingly (janglers and jappers respectively), sleepers (nappers), yawners (galpers), drawlers (drawers), mumblers (momlers), those who skip over things (fore-skippers), those who overrun things (over-enders) and those that simply foreskip with a bounce (over-hoppers).

"At some point in the 15th century the scribes, overworked by the demands put on them by the universities' need for texts, disclaimed responsibility for the errors in the manuscripts they had to rush to produce. Titivillus, they said, had tempted them to err. And Titivillus, acknowledged as the cause of their errata, became a patron rather than a pest since he absolved them of their guilt."2

1ref. A Catalogue of the Lansdowne Manuscripts in the British Museum London, 1819

2ref. Medieval Calligraphy - It's History and Technique Marc Drogin