Question: During the Middle Ages, in Germany, people believed that kissing a donkey would do what?
Answer: During the Middle Ages in Germany, people believed that kissing a donkey relieved toothaches.
Kissing a donkey to cure toothache
In German legend from the Middle Ages it was proposed that kissing a donkey would take away the pain of toothache. It can only be presumed that attempting this with a member of the horse family could lead to an act of aggression resultant in accidental exodontia, thus removing the painful tooth and source of toothache.