The Gibberling is a monster from AD&D. My information comes from the 1996 printing of the Monstrous Manual, and my own personal experience DMing the creatures.
Gibberling are pale, hunchbacked humanoids, who resemble apes with canine heads and black manes. Their eyes are black and shine with a maniacal gleam. It is unclear how, or when, or even if Gibberlings procreate.
A single Gibberling is unimpressive, standing only 4 to 5 feet tall. Gibberlings are also of low intelligence. The creatures carry poorly worked short swords, and it is unknown where they get them. However, no Gibberling is ever encountered alone. Instead, they are found in packs of 40 to as many as 400. These packs move by night, in a screaming mob, without direction or thought. All food in their path is devoured, including their own dead. Gibberlings have no sense, organization, or individuality. They clearly have a means of communication, but no discernable language. During the day the swarm burrows into the ground, and it is at this time that they are most vulnerable.
The oncoming horde of screaming Gibberlings is enough to unnerve even the stoutest adventurer, and cause most of his henchmen and hirelings to run in fear. Gibberlings have a strong fear of light, so the best method for stopping them is probably to either build a bonfire, or utilize some form of magical light.