The Collaborative International Dictionary of English v.0.48:

Inn \Inn\ ([i^]n), n. [AS. in, inn, house, chamber, inn, from
   AS. in in; akin to Icel. inni house. See In.]
   1. A place of shelter; hence, dwelling; habitation;
      residence; abode. [Obs.] --Chaucer.
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            Therefore with me ye may take up your inn
            For this same night.                  --Spenser.
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   2. A house for the lodging and entertainment of travelers or
      wayfarers; a tavern; a public house; a hotel.
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   Note: As distinguished from a private boarding house, an inn
         is a house for the entertainment of all travelers of
         good conduct and means of payment, as guests for a
         brief period, not as lodgers or boarders by contract.
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               The miserable fare and miserable lodgment of a
               provincial inn.                    --W. Irving.
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   3. The town residence of a nobleman or distinguished person;
      as, Leicester Inn. [Eng.]
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   4. One of the colleges (societies or buildings) in London,
      for students of the law barristers; as, the Inns of Court;
      the Inns of Chancery; Serjeants' Inns.
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   Inns of chancery (Eng.), colleges in which young students
      formerly began their law studies, now occupied chiefly bp
      attorn`ys, solocitors, etc.

   Inns of court (Eng.), the four societies of "students and
      practicers of the law of England" which in London exercise
      the exclusive right of admitting persons to practice at
      the bar; also, the buildings in which the law students and
      barristers have their chambers. They are the Inner Temple,
      the Middle Temple, Lincoln's Inn, and Gray's Inn.
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Bouvier's Law Dictionary, Revised 6th Ed (1856):

INNS OF COURT, Engl. law. The name given to the colleges of the English
professors and students of the common law. 2. The four principal Inns of
Court are the Inner Temple and Middle Temple, (formerly belonging to the
Knights Templars) Lincoln's Inn, and Gray's Inn, (ancient belonging to the
earls of Lincoln and ray.) The other inns are the two Sergeants' Inns. The
Inns of Chancery were probably so called because they were once inhabited by
such clerks, as chiefly studied the forming of writs, which regularly
belonged to the cursitors, who are officers of chancery. These are Thavie's
Inn, the New Inn, Symond's Inn, Clement's Inn, Clifford's Inn,' Staple's
Inn, Lion's Inn, Furnival's Inn and Barnard's Inn. Before being called to
the bar, it is necessary to be admitted to one of the Inns of Court.