The Collaborative International Dictionary of English v.0.48:

Demain \De*main"\, n. [See Demesne.]
   1. Rule; management. [Obs.] --Chaucer.
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   2. (Law) See Demesne.
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The Collaborative International Dictionary of English v.0.48:

Demesne \De*mesne"\, n. [OE. demeine, demain, rule, demesne, OF.
   demeine, demaine, demeigne, domaine, power, F. domaine
   domain, fr. L. dominium property, right of ownership, fr.
   dominus master, proprietor, owner. See Dame, and cf.
   Demain, Domain, Danger, Dungeon.] (Law)
   A lord's chief manor place, with that part of the lands
   belonging thereto which has not been granted out in tenancy;
   a house, and the land adjoining, kept for the proprietor's
   own use. [Written also demain.] --Wharton's Law Dict.
   Burrill.
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   Ancient demesne. (Eng. Law) See under Ancient.
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