More than 10 years have passed since the birth of The Attack of the Giants, a manga that suggested a unique story and has become one of the most popular of the past decade. Over time, Hajime Isayama asked many questions, which he then slowly solved. One of them is this Birth of the power of giants.
We now know that the nine giants exist, creatures other than pure giants, and have special abilities. But how these creatures from Attack of the Giants were born and that is still fundamental to the plot of Hajime Isayama's manga today? The explanation was given by the author, but at the moment the relevant chapter has not yet been translated into anime. So if you're not on par with the comic, the rest of the content will be spoilers.
There The answer lies in chapter 122 of The Giants' Attack, entitled "From you, 2000 years ago" and which explicitly refers to the first chapter. Here we come to a connection with Ymir, the ancestor of the power of the giants and one of the most famous figures of the ancient Eldian Empire. The reality is that Ymir was initially a simple slave who, for random reasons, at the time of death came into contact with a mysterious creature that gave her the power of giants.
Taken as wife by the king of the Eldian tribe, she fathered three daughters who ate her flesh and spinal fluid after her death. From this gesture began the division of his powers and that led to the creation of the nine giants.