The Collaborative International Dictionary of English v.0.48:

Dop \Dop\, Doop \Doop\, n.
   A little copper cup in which a diamond is held while being
   cut.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dop \Dop\, v. i. [Cf. Dap, Dip.]
   To dip. [Obs.] --Walton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dop \Dop\, n.
   A dip; a low courtesy. [Obs.] --B. Jonson.
   [1913 Webster]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

DOP
       Directory Operational binding management Protocol