dies Dominica

From diēs (“day”) +‎ dominica (“of the Lord (adj.)”). Since the head-noun diēs could be either masculine or feminine, the phrase has a masculine counterpart in diēs Dominicus.

Found in Late Latin as a Christian replacement for the pagan diēs Sōlis (“Sunday”, literally “day of the sun-god Sol”). Completely erased the latter, as far as Romance is concerned.

• (Classical) IPA^(key): /ˈdi.eːs doˈmi.ni.ka/, [ˈd̪ieːs̠ d̪ɔˈmɪnɪkä]
• (Ecclesiastical) IPA^(key): /ˈdi.es doˈmi.ni.ka/, [ˈd̪iːes d̪oˈmiːnikä]

diēs Dominica f (genitive diēī Dominicae); fifth declension

1. (Late Latin) Sunday
   • late 4th c. CE, Egeria, Peregrinatio ad loca sancta 2.25:

     Cum luce autem, quia dominica dies est, et proceditur in ecclesia maiore, quam fecit Constantinus, quae ecclesia in Golgotha est post Crucem, et fiunt omnia secundum consuetudinem, qua et ubique fit die dominica.

     At dawn, however, as it is Sunday, the people go to the greater church built by Constantine, located in Golgotha behind the Cross. They carry out everything that is usual everywhere on Sunday.

Fifth-declension noun with a first-declension adjective.

• diēs Sōlis
• Dominica

See also diēs Dominicus.
All Romance descendants reflect a shortening to dominica.

• Walther von Wartburg (1928–2002), “domĭnicus”, in Französisches Etymologisches Wörterbuch (in German), volume 3: D–F, page 129
• AIS: Sprach- und Sachatlas Italiens und der Südschweiz [Linguistic and Ethnographic Atlas of Italy and Southern Switzerland] – map 335: “domenica” – on navigais-web.pd.istc.cnr.it