Babbling Curse

From Harry Potter Wiki

Babbling Curse
Type:	Curse
Effect:	Causes uncontrollable babbling

The Babbling Curse (incantation unknown) is not fully understood but it is presumed to cause a person to babble whenever they try to speak. According to Gilderoy Lockhart, he once cured a Transylvanian villager of this affliction, but as he proved an untrustworthy source of information, it is possible the curse does not exist at all. However, the curse itself may exist, but it could be that someone else cured the said villager.