Why is it called daughters of mnemosyne?

Mnemosyne, in Greek mythology was the goddess of memory. She was a Titan female, the daughter of Heaven and Earth. It is also said she was the mother of the nine Muses, with Zeus as the father. In short- she was the Goddess of Memory, and her daughters were the Muses....

In the series, only females became immortal- via the "Time Fruit" orbs(as their mother would have been), and I would assume remember "everything" with such a long lifespan. From there, I don't understand the correlation between the series and the mythology, aside from the idea that perhaps the Yggdrasil tree was a symbol of the Goddess Mnemosyne. Or perhaps just a metaphor of sorts that the Immortals will always remember. But I say this, using my own ideals and understanding between the definition of Mnemosyne, and knowing the characters in an English-dubbed series. ^_^