WordNet (r) 3.0 (2006):

DDT
    n 1: an insecticide that is also toxic to animals and humans;
         banned in the United States since 1972 [syn:
         dichlorodiphenyltrichloroethane, DDT]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "DDT":
   DDD, Paris green, antimony, arsenic, arsenic trioxide, beryllium,
   bichloride of mercury, cadmium, carbolic acid, carbon monoxide,
   carbon tetrachloride, chlorine, cyanide, hydrocyanic acid,
   hyoscyamine, lead, mercuric chloride, mercury, mustard gas,
   nicotine, phenol, poison gas, prussic acid, selenium, strychnine



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

DDT
       Dynamic Debugging Tool (DEC, CP/M)


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

DDT
 /D?D?T/, n.

    [from the insecticide para-dichloro-diphenyl-trichloroethene]

    1. Generic term for a program that assists in debugging other programs by
    showing individual machine instructions in a readable symbolic form and
    letting the user change them. In this sense the term DDT is now archaic,
    having been widely displaced by debugger or names of individual programs
    like adb, sdb, dbx, or gdb.

    2. [ITS] Under MIT's fabled ITS operating system, DDT (running under the
    alias HACTRN, a six-letterism for ?Hack Translator?) was also used as the 
    shell or top level command language used to execute other programs.

    3. Any one of several specific DDTs (sense 1) supported on early DEC
    hardware and CP/M. The PDP-10 Reference Handbook (1969) contained a
    footnote on the first page of the documentation for DDT that illuminates
    the origin of the term:

        Historical footnote: DDT was developed at MIT for the PDP-1 computer in
        1961. At that time DDT stood for ?DEC Debugging Tape?. Since then, the
        idea of an on-line debugging program has propagated throughout the
        computer industry. DDT programs are now available for all DEC
        computers. Since media other than tape are now frequently used, the
        more descriptive name ?Dynamic Debugging Technique? has been adopted,
        retaining the DDT abbreviation. Confusion between DDT-10 and another
        well known pesticide, dichloro-diphenyl-trichloroethane C[14]H[9]Cl[5]
        should be minimal since each attacks a different, and apparently
        mutually exclusive, class of bugs.

    (The ?tape? referred to was, incidentally, not magnetic but paper.) Sadly,
    this quotation was removed from later editions of the handbook after the 
    suits took over and DEC became much more ?businesslike?.

    The history above is known to many old-time hackers. But there's more:
    Peter Samson, compiler of the original TMRC lexicon, reports that he
    named DDT after a similar tool on the TX-0 computer, the direct ancestor of
    the PDP-1 built at MIT's Lincoln Lab in 1957. The debugger on that
    ground-breaking machine rejoiced in the name FLIT (FLexowriter
    Interrogation Tape). Flit was for many years the trade-name of a popular
    insecticide.


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

DDT

   1. Generic term for a program that assists in debugging other
   programs by showing individual machine instructions in a
   readable symbolic form and letting the user change them.  In
   this sense the term DDT is now archaic, having been widely
   displaced by "debugger" or names of individual programs like
   "adb", "sdb", "dbx", or "gdb".

   2. Under MIT's fabled ITS operating system, DDT (running
   under the alias HACTRN) was also used as the shell or top
   level command language used to execute other programs.

   3. Any one of several specific debuggers supported on early
   DEC hardware.  The DEC PDP-10 Reference Handbook (1969)
   contained a footnote on the first page of the documentation
   for DDT that illuminates the origin of the term:

   Historical footnote: DDT was developed at MIT for the
   PDP-1 computer in 1961.  At that time DDT stood for "DEC
   Debugging Tape".  Since then, the idea of an on-line debugging
   program has propagated throughout the computer industry.  DDT
   programs are now available for all DEC computers.  Since media
   other than tape are now frequently used, the more descriptive
   name "Dynamic Debugging Technique" has been adopted, retaining
   the DDT abbreviation.  Confusion between DDT-10 and another
   well known pesticide, dichloro-diphenyl-trichloroethane
   (C14-H9-Cl5) should be minimal since each attacks a different,
   and apparently mutually exclusive, class of bugs.

   (The "tape" referred to was, incidentally, not magnetic but
   paper.)  Sadly, this quotation was removed from later editions
   of the handbook after the suits took over and DEC became
   much more "businesslike".

   The history above is known to many old-time hackers.  But
   there's more: Peter Samson, compiler of the original TMRC
   lexicon, reports that he named "DDT" after a similar tool on
   the TX-0 computer, the direct ancestor of the PDP-1 built at
   MIT's Lincoln Lab in 1957.  The debugger on that
   ground-breaking machine (the first transistorised computer)
   rejoiced in the name FLIT (FLexowriter Interrogation Tape).

   [Jargon File]