The Babbling Curse causes the victim to babble nonsense.
References from the canon
- Lockhart supposedly cured a simple Transylvanian villager of this affliction (CS10). As always with Lockhart's bragging, this spell (and the cure) may not exist.
Lockhart supposedly encountered the Babbling Curse in Transylvania, so we can probably assume he wrote about it in his book Voyages With Vampires.
From the Web
"Babbling Curse" from Harry Potter Wiki