His mother was Maia.

In Greek mythology Maia was one of the seven Pleiades or mountain nymphs. She is the mother of Hermes the god of transitions and boundaries. His father was Zeus.

In greek mythology she was the mother of hermes. Maia is the daughter of Atlas and Pleione the oceanid they were born on Mount Cyllene and are ometimes called mountain nymphs

A Pleiades daughter of Atlas and Pleione, and the mother of Hermes.

Maia is just the activation word for the flying shoes Luke gives to Percy. In Greek mythology, Hermes' mother's name is Maia, which may be why that's the activation word. It's not mentioned in the books, though.