In the Middle Ages, the demon tutivillus was known to introduce errors into the work of scribes copying texts, later with the invention of the printing press causing typesetters to make typesetting errors. So ubiquitously known was tutivillus as demon for literacy, he was painted on church walls and carved into pews and chairs to ward him away.
Pious tradition abound exist of the exploits of tutivillus, the most well known of which where he gathers up all “syalablys & woordys, ouerskipped and synkopyed, & verse & psalymys þe whiche þese clerkys han stolyn in þe qweere, & haue fayled in here seruyse” of preaching priests into a sack. The story continues that after a priest dies, they must carry sacks full of words they mispronounced during Mass in Hell.
Another traditions tells of common occurrence when a priest would see tutivillus “perched high up in a church noting down the idle gossip of parishioners who are chattering rather than paying attention to the Mass; the people talk so much that he must stretch out his parchment with his teeth in order to fit all the words on it; in many versions the parchment breaks, Tutivillus bangs his head on the wall or pillar of the church and the priest laughs and warns the congregation, who usually repent and oblige the demon to erase what he has written.”
How would scribes protect their work once finished? By placing a curse on it, of course. Read more about the little-known Medieval “manuscript curse” here.