The association between Saturday and Saturn is likely due to the fact that Saturn was the slowest-moving planet known to the ancient Romans. This led them to believe that it had a special connection to time and agriculture, which were both important aspects of their society.
In some cultures, Saturday is also associated with other gods or goddesses. For example, in Norse mythology, Saturday is named after the god Tyr, who was associated with war and law. In Hinduism, Saturday is associated with the god Shani, who is associated with justice and retribution.
Overall, the mythological meaning of Saturday is one of time, agriculture, and justice.