The Collaborative International Dictionary of English v.0.48:

Dup \Dup\ (d[u^]p), v. t. [Contr. fr. do up, that is, to lift up
   the latch. Cf. Don, Doff.]
   To open; as, to dup the door. [Obs.] --Shak.
   [1913 Webster]

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

DUP
       Distribution Unit Profile (MS, OSD, DU, MSIE)