Sabbatarian (n.) Look up Sabbatarian at Dictionary.com
1610s, "a Christian unusually strict about Sabbath observation," from Latin Sabbatarius (adj.), from Sabbatum (see Sabbath). Meaning "member of a Christian sect which maintained the Sabbath should be observed on the seventh day" is attested from 1640s; earlier sabbatary (1590s). Related: Sabbatartianism.