The gentle rocking back and forth of the moon, over a given time period, is called libration. Even though, the front of the Moon is tidally locked to always face towards Earth, this phenomena allows an observer on Earth to see close to 60% of the lunar surface.
The ancient Greek Deity for the moon was Selene; hence selenology, the study of the geology of the Moon. Whereas her brother, Helios, was the personification of the other celestial body, the Sun.
Since the the second lightest and the second most abundant element in the observable Universe was first discovered using a mass spectrometer on sunlight, it's only fitting that it would have the name Helium.