The Collaborative International Dictionary of English v.0.48:

Derrick \Der"rick\, n. [Orig., a gallows, from a hangman named
   Derrick. The name is of Dutch origin; D. Diederik, Dierryk,
   prop. meaning, chief of the people; cf. AS. pe['o]dric, E.
   Theodoric, G. Dietrich. See Dutch, and Rich.]
   1. A mast, spar, or tall frame, supported at the top by stays
      or guys, and usually pivoted at the base, with suitable
      tackle for hoisting heavy weights, such as stones in
      building.
      [1913 Webster]

   2. (Mining) The pyramidal structure or tower over a deep
      drill hole, such as that of an oil well (also called an
      oil derrick .
      [Webster 1913 Suppl. +PJC]

   Derrick crane, a combination of the derrick and the crane,
      having facility for hoisting and also for swinging the
      load horizontally.
      [1913 Webster]

WordNet (r) 3.0 (2006):

derrick
    n 1: a framework erected over an oil well to allow drill tubes
         to be raised and lowered
    2: a simple crane having lifting tackle slung from a boom