WordNet (r) 3.0 (2006):

thunk
    n 1: a dull hollow sound; "the basketball made a thunk as it hit
         the rim"

The Jargon File (version 4.4.7, 29 Dec 2003):

thunk
 /thuhnk/, n.

    1. [obs.]?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. Microsoft and IBM have both defined, in their Intel-based systems, a ?
    16-bit environment? (with bletcherous segment registers and 64K address
    limits) and a ?32-bit environment? (with flat addressing and semi-real
    memory management). The two environments can both be running on the same
    computer and OS (thanks to what is called, in the Microsoft world, WOW
    which stands for Windows On Windows). MS and IBM have both decided that the
    process of getting from 16- to 32-bit and vice versa is called a ?thunk?;
    for Windows 95, there is even a tool THUNK.EXE called a ?thunk compiler?.

    5. A person or activity 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?.


The Free On-line Dictionary of Computing (30 December 2018):

thunk

    /thuhnk/ 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. The term was later generalised to mean an expression,
   frozen together with its environment (variable values), for
   later evaluation if and when needed (similar to 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.

   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 realised (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".

   4. (Microsoft Windows programming) universal thunk,
   generic thunk, flat thunk.

   [Jargon File]

   (1997-10-11)