I really enjoyed "Spock Must Die!" and I loved Blish's reference to the transporter using DIRAC technology (from his short story of the same name)
Dirac isn't an acronym. Blish was referring to physicist Paul Dirac
, one of the pioneers of quantum mechanics -- he's literally the man who wrote the book on the subject. What Blish called a Dirac jump in SMD! was basically what's known as a "quantum leap," and the instantaneous "Dirac communicator" used in much of Blish's work was basically a quantum-entanglement device (much the same sort of thing that Ursula LeGuin's term "ansible" is often applied to). Blish was basically using Dirac's name as a metonym for quantum theory.