The proper Sumerian form of the name is UDUG; Utukku is the Akkadian form. It is common to change /D/ to /t/ and /G/ to /k/ in converting Sumerian into Akkadian. The final /-u/ is the Akkadian nominative case-ending.
The canon of exorcism of the evil UDUG is known as UDUG HUL, the Akkadian expansion of which (known in Akkadian as Utukkū Lemnūtu) is in sixteen tablets.
They were siblings of the Anunnaki. They were in the service of the underworld, and were required to fetch home the fruit of the sacrifices and burnt offerings, which generally consisted of the blood, liver, and other "sweetmeats" of the sacrificed animal.
The following passage quoted by Langdon shows the modus operandi of the Utukku: The wicked Utukku who slays man alive on the plain. The wicked Alû who covers (man) like a garment. The wicked Etimmu, the wicked Gallû, who bind the body. The Lamme (Lamashtu), the Lammea (Labasu), who cause disease in the body. The Lilû who wanders in the plain. They have come nigh unto a suffering man on the outside. They have brought about a painful malady in his body. The curse of evil has come into his body. An evil goblin they have placed in his body. An evil bane has come into his body. Evil poison they have placed in his body. An evil malediction has come into his parts. Evil and trouble they have placed in his body. Poison and taint have come into his body. They have produced evil. Evil being, evil face, evil mouth, evil tongue. Sorcery, venom, slaver, wicked machinations, Which are produced in the body of the sick man. O woe for the sick man whom thy cause to moan like a šąharrat (pot).--(Langdon, 357, 362, 364)