The Collaborative International Dictionary of English v.0.48:

Equerry \Eq"uer*ry\ (?; 277), n.; pl. Equerries. [F. ['e]curie
   stable, for older escurie, escuirie (confused somewhat with
   F. ['e]cuyer, OF. escuyer, squire), LL. scuria, OHG. skiura,
   sc?ra, barn, shed, G. scheuer, from a root meaning to cover,
   protect, and akin to L. scutum shield. See Esquire, and cf.
   Ecurie, Querry.]
   1. A large stable or lodge for horses. --Johnson.
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   2. An officer of princes or nobles, charged with the care of
      their horses.
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   Note: In England equerries are officers of the royal
         household in the department of the Master of the Horse.
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