The Okie flying cities are based on two technological advances, spindizzies and anti-agathics, so that, in this case, the one word splits into two others. The Okies also use the Dirac communicator though not in the same way as in the Dirac series.
After Such Knowledge is a thematic not a linear trilogy. Thus, each of its volumes has a different defining word: Bacon, demons and Lithia.
In the Middle Ages, Roger Bacon sought knowledge through observation and experiment;
in the twentieth century, Theron Ware sought knowledge by controlling demons;
in 2049, a UN science team will gather knowledge on the planet Lithia.
Thus, two of the key words are names of scientists, Bacon and Dirac. However, Doctor Mirabilis is a biographical novel about Bacon whereas the Dirac series features a fictitious instantaneous communicator named after Paul Dirac.
Two other significant scientists are the historical Einstein, whose theory must be surpassed if there is to be faster than light travel to Lithia or to anywhere else, and the fictitious Haertel, whose theory does surpass Einstein's. The telepathy, Angels and Dirac series and the Lithia novel all refer to Haertel who thus achieves a role in Blish's fictitious histories comparable to that of Einstein in our history.