Sunday gets its name from the Old English "Sunnandæg," which literally means "Sun's day."
This naming comes from ancient Roman and Germanic traditions, where each day of the week was associated with a celestial body and a corresponding god. Sunday was dedicated to the Sun, which was seen as a powerful and divine force.
The Romans called it "dies Solis" (day of the Sun), and when Germanic peoples adopted the Roman system, they translated it into their own languages — leading to "Sunnandæg" in Old English.