In Greek mythology, Phaethusa ("radiance") was a daughter of Helios and Neaera, the personification of the brilliant, blinding rays of the sun. With her sister, Lampetia, she guarded the cattle of Thrinacia[?].
... the groove, the friction between the axis and the groove rims will accelerate or brake the spinning gyroscope, with a maximum effect when the axis starts "rolling" ...