The word comes from the Koine Greek κοσμογονία (from κόσμος "cosmos, the world") and the root of γί(γ)νομαι / γέγονα ("come into a new state of being"). In astronomy, cosmogony refers to the study of the origin of particular astrophysical objects or systems, and is most commonly used in reference to the origin of the universe, the solar system, or the earth-moon system.