Meaning

noun extensive landed property (especially in the country) retained by the owner for his own use

noun territory over which rule or control is exercised

originFrom Middle English demayne, from Anglo-Norman demeyne, demene et al., Old French demeine, demaine, demeigne, domaine (“power”) (whence French domaine (“domain”)), a noun use of an adjective, from Latin dominicus (“belonging to a lord or master”), from dominus (“master, proprietor, owner”). See dame. Doublet of domain. The spelling with non-etymological s is partly due to influence from mesne and…

Etymology from Wiktionary, CC BY-SA 3.0