From Wikipedia
Rumors abound as to what the letters DDT supposedly stood for, including Drape Drop Takedown, Drop Dead Twice, Definitely Dead Tomorrow, Demonic Death Trap, Drop Down Town, Death Drop Technique and Damien's Dinner Time or Damien's Death Touch (the latter two named after Jake's pet python Damien). When asked what DDT meant, Jake once famously replied "The End."[4] The abbreviation itself originally came from the chemical dichloro-diphenyl-trichloroethane, a notorious pesticide, as stated during shoot interviews and Jake's Pick Your Poison DVD. Many think that the term DDT was applied because the chemical DDT is a hazardous chemical buried in the ground which potentially causes brain damage.