Mummies

Mummies are a type of undead first found in fiction of the 19th century and made a definite part of the horror scene with the 1932 movie The Mummy. Usually, "mummy" is understood to mean the Egyptian royal variety, but any dead body of which the soft tissue has been preserved is qualified to be called a mummy.

Etymology
The word "mummy" comes from "mummia", a collective term for any substance used in the Ancient Egyptian mummy-making and any substance made from Ancient Egyptian mummies. "Mummia" itself comes from the Persian word "موم", "mum", which means "bitumen", "asphalt". Bitumen was thought to be used in the mummification process due to bitumen being black and mummies having blackened skin, but research has revealed that if there's even bitumen in the mummy, it most likely got there coincidentally, not intentionally. Bitumen was, however, popularly used in the second millenium to produce fake ancient mummies.

The word "mummy" originally (ca. 1400) referred to the process of mummification, but around 1650 it came to refer to the mummified body too. In the next hundred years, the term's meaning was expanded to "any dead body of which the soft tissue has been preserved".

Ancient Egyptian mummies and the rest
Mummification is a process that can happen due to natural circumstances or due to human action. Examples of naturally formed mummies are the bog bodies of northwestern Europe, which have been mummified by the acidity, low temperature, and oxygen-free environment of the bogs, the Tarim mummies of China, which have been mummified due to a dry and saline environment of the Tarim Basin, and the Llullaillaco mummies, which have been mummified due to the cold at the summit of Llullaillaco.

Mummification as a result of human action developed first in areas where mummification was prone to happen naturally and thus could inspire the locals to develop mummification techniques. The oldest known deliberate mummy dates from around 5050 BC and was found in the Camarones Valley in Chile. Needless to say, as time went on mummification techniques became more refined and diverse as they spread to other tribes and nations. Most practices on mummification are no longer in use, but mummies are still made to this day, such as with plastination, which has the water and fat from bodies replaced with plastics.

Ancient Egyptian incorporation of mummification in burial rites appears to have its origin in the city of Nekhen around 3500 BC. A mummy from the same time period was found in Uan Muhuggiag, Libya. This mummy was preserved with techniques more advanced than the Nekhen ones and several artifacts found at the burial site, such as art depicting humans with animal masks, suggests that the Ancient Egyptians were inspired by customs from their western neighbors.

Mummies in Monster High
The Monster High mummies are Mr. Mummy and the De Nile family, consisting of at least of Cleo de Nile, Nefera de Nile, and their father, who is called Ramses de Nile in the books. Referred to in the Dawn of the Dance diaries and on Facebook is the girls' uncle Tut, and the books make mention of an aunt named Nefetiti.

Cleo de Nile is roughly 5,842 years old and her sister Nefera roughly 5,845 years. This means that in the Monster High universe, Ancient Egypt and its mummification practices kicked off well before they did in the real world. According to Cleo de Nile's School's Out Diary, she and her family lost their throne due to betrayal by people they trusted. This presumably led to the family being mummified and entombed for nearly 6,000 years, from which Cleo emerged with a severe case of fear of the dark, as noted in her Basic diary.