Chastellenie : A Castle-wick, or Castleship; the Tenure or Honour of a Castleship ; the Estate, Jurisdiction, or Dignity of a Lord Castellain; a kind of Seigniory that’s held of some other than the King, or not directly of the Crown, and hath all (subaltern) Jurisdiction annexed unto it.
A Dictionarie of the French and English Tongue
London: Adam Islip, 1611
[from med Latin, castellainia, castle] The office or jurisdiction of a castellan; the lordship of a castle, or the district belonging to a castle. First example from 1357.
A castellan was the governor or caretaker of a castle or keep. Usually, a castellan combined the duties of both a majordomo (responsible for a castle’s domestic staff) and a military administrator (responsible for maintaining defenses and protecting the castle’s lands). This was particularly the case if there was no lord resident at the castle, or if the resident lord was frequently absent. In France, castellans (known in French as Châtelains) who governed castles without resident nobles acquired considerable powers, and the position actually became a hereditary fiefdom.