An excerpt from Trusted Translations explaining the origins of the days of the week:
“From as early as the first century, the Romans utilized Saturday as the first day of their week. However, because they worshipped the Sun, they began using that day, Sunday, as the first day of the week. Its origin is tied to the Latin phrase for ‘sun’s day’ (dies solis). In Latin, it is also said as dominica, which is the ‘Day of God.’ In Spanish, domingo, French, dimanche, Italian, domenica.”