thunk

thunk /thuhnk/ n.  1. "A piece of coding which provides
   an address", according to P. Z. Ingerman, who invented thunks in
   1961 as a way of binding actual parameters to their formal
   definitions in Algol-60 procedure calls.  If a procedure is called
   with an expression in the place of a formal parameter, the compiler
   generates a thunk which computes the expression and leaves the
   address of the result in some standard location.  2. Later
   generalized into: an expression, frozen together with its
   environment, for later evaluation if and when needed (similar to
   what in techspeak is called a `closure').  The process of
   unfreezing these thunks is called `forcing'.  3. A
   {stubroutine}, in an overlay programming environment, that loads
   and jumps to the correct overlay.  Compare {trampoline}.
   4. People and activities scheduled in a thunklike manner.  "It
   occurred to me the other day that I am rather accurately modeled by
   a thunk -- I frequently need to be forced to completion." ---
   paraphrased from a {plan file}.

   Historical note: There are a couple of onomatopoeic myths
   circulating about the origin of this term.  The most common is that
   it is the sound made by data hitting the stack; another holds that
   the sound is that of the data hitting an accumulator.  Yet another
   suggests that it is the sound of the expression being unfrozen at
   argument-evaluation time.  In fact, according to the inventors, it
   was coined after they realized (in the wee hours after hours of
   discussion) that the type of an argument in Algol-60 could be
   figured out in advance with a little compile-time thought,
   simplifying the evaluation machinery.  In other words, it had
   `already been thought of'; thus it was christened a `thunk',
   which is "the past tense of `think' at two in the morning".