A morning star is a bright planet, usually Venus, that appears in the eastern sky just before sunrise. Ancient peoples noticed this brilliant point of light and gave it special names, not realizing they were looking at a planet rather than a star. Venus shines so brightly in the pre-dawn darkness that it often remains visible even as the sky begins to lighten.

The same planet appears as the “evening star” when it's visible after sunset in the western sky, though people long ago didn't realize these were the same object. Venus takes different positions relative to Earth and the Sun throughout the year, which is why it sometimes appears in the morning and sometimes in the evening, but never in the middle of the night.

The term also refers to a medieval weapon: a spiked metal ball attached to a handle by a chain. Warriors would swing this weapon in circles to build momentum before striking. The weapon got its name because the spikes radiating from the ball resembled the bright rays of light that seemed to shoot out from Venus in the dawn sky.