The Collaborative International Dictionary of English v.0.48:

Demit \De*mit"\, n.
   The act of demitting; also, a letter, certificate, or the
   like, certifying that a person has (honorably) demitted, as
   from a Masonic lodge.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Demit \De*mit"\, v. t. [imp. & p. p. Demitted; p. pr. & vb. n.
   Demitting.] [L. demittere to send or bring down, to lower;
   de- + mittere to send. Cf. Demise.]
   1. To let fall; to depress. [R.]
      [1913 Webster]

            They [peacocks] demit and let fall the same [i. e.,
            their train].                         --Sir T.
                                                  Browne.
      [1913 Webster]

   2. To yield or submit; to humble; to lower; as, to demit
      one's self to humble duties. [R.]
      [1913 Webster]

   3. To lay down, as an office; to resign. [Scot.]
      [1913 Webster]

            General Conway demitted his office.   --Hume.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Demit \De*mit"\, v. i. [F. d['e]mettre to remove, se d['e]mettre
   to resign; d['e]- (L. dis-) + mettre to put, fr. L. mittere
   to send. Cf. Dismiss.]
   To lay down or relinquish an office, membership, authority,
   or the like; to resign, as from a Masonic lodge; -- generally
   used with an implication that the act is voluntary.
   [Webster 1913 Suppl.]