From domnia, from domn, from Latin dominus (“master”) + voastră, from Latin voster, vostra (“your”), thus initially meaning "your lordship". Compare similar constructions in Spanish usted (“you”) from vuestra merced (cf. also vuecencia), Portuguese você (“you”), Catalan vostè, etc.
dumneavoastră
Dumneavoastră (abbreviated as dv., dvs., or d-voastră) is used in polite or formal speech in place of the plain pronouns tu and voi. Dumneavoastră always takes verbs in the second person plural forms, that is, the same forms as voi. For example, dumneavoastră sunteți and voi sunteți both mean "you are," but the former is polite and can take singular and plural meanings, whereas the second is informal and only used in the plural. Dumneavoastră has the same form in the genitive and dative cases as in the nominative and accusative.
Dumneavoastră is also the plural of dumneata, a semi-polite pronoun.