The term is an act of snobbery from the Egyptian mummies, because each of their original groups had an age and a lineage. The Shemsu-Heru were the first Dynasty, the true Undying created by and for the Gods to wage a holy war against Apophis. Then came the turncoats of the Ishmaelites, the second dynasty, created by a desire for freedom and self-determination. The third dynasty were the cursed Apepnu, servants of Apophis raised by the Bane rite of the enemy Set and finally came the bastard thieves of immortality, the fourth Dynasty of the Cabiri. When the Undying of the Spell of Life became aware of other Immortals from other lands, they naturally fell into calling them Dynasties. When the Sixth Maelstrom ravaged the Underworld and the new Spell of Life was spoken, new dynasties were created that were collectively known as the Amenti.
As recent events lead to innovations in the previous Spells of Life that powered the old, imperfect mummies, new dynasties spread. The old mummies are seen as Shuankhsen, hunted by the Hand of Thoth or in the service of Apophis. Likewise, the Capacocha have renovated the Spell of Going Westward in order to reclaim their bodies and became the Teomallki.