astronomy

Greek astron is a star. Greek nomos is law, custom, the way something is arranged. Astronomia is the arranging of the stars: not yet a modern science with observatories and orbits, but a name for putting the heavens in order.

English borrowed the finished Greek word. The cut astro + nomy is a historical reading of that Greek compound. It is not an English pattern for inventing new sciences at the kitchen table.

For a long stretch of history, this ordering sat beside astrology, the reading of meaning in the same sky. The two words share a star. Their quarrel is later than their root.