The Collaborative International Dictionary of English v.0.48:

Interrogate \In*ter"ro*gate\, v. t. [imp. & p. p.
   Interrogating.] [L. interrogatus, p. p. of interrogare to
   ask; inter between + rogare to ask. See Rogation.]
   To question formally; to question; to examine by asking
   questions; as, to interrogate a witness.
   [1913 Webster]

         Wilt thou, uncalled, interrogate,
         Talker! the unreplying Fate?             --Emerson.

   Syn: To question; ask. See Question.
        [1913 Webster]