The Collaborative International Dictionary of English v.0.48:

Dedimus \Ded"i*mus\, n. [L. dedimus we have given, fr. dare to
   give. So called because the writ began, Dedimus potestatem,
   etc.] (Law)
   A writ to commission private persons to do some act in place
   of a judge, as to examine a witness, etc. --Bouvier.
   [1913 Webster]