Now the Abbess starts arguing about mortal sins (those are the really bad ones) and the venial ones (not so bad). She decides that if they each say only part of the word, then neither will be sinning. So they split the words in two and each take part.
The Abbess says "bou" and Margarita, the novice, says "ger"; then Margarita says "fou" and the Abbess says "ter." (Random curse words—always a good way to get mules going).
They say the words faster and faster, but the mules don't hear them—only the devil does.