Saturday is named after Saturn, the Roman god of agriculture, time, and harvest. The Romans named their sixth day of the week dies Saturni, meaning "Saturn's day." This name was later adopted into English and other Germanic languages.
While most of the days of the week are named after Norse gods (Tuesday - Thursday), Saturday retains its Roman origin. This is because the Roman calendar and its influence on the naming of the days of the week were more prominent during the early development of English.
