https://en.wikipedia.org/wiki/Names_of_the_days_of_the_week.
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The Wikipedia article lists the names of the days of the week in many languages, which link to articles explaining where the name came from. It also describes the numbering of the days in the week, which varies according to language.
A number of European languages derived the name for Saturday from the Greek word for "Sabbath". In addition, Romance languages tend to derive the name of Sunday from "The Lord's Day" while also naming Saturday after the Sabbath. Though Scandinavian languages call Saturday "Bath Day"; bathe once a week whether you need it or not.
Edited by dwise1, : explanation