Ralph Brave, "Germline warfare," The Nation, April 7, 2003
Bruce Sterling, Schismatrix, 1985
The second method involves altering the existing genes of a fertilized egg. Such an egg is called a germ cell, so this method is known as germline genetic engineering.
The path to a posthuman world does not go through somatic gene therapy since that technique (which is already in clinical trials) only works on individuals: the genetic modifications are not passed on to the person's offspring. Germline tinkering, on the other hand, modifies the person's genetic makeup, and that makeup gets passed on to all of that person's descendants. Make enough modifications vastly improved hearing, strength, endurance, and so on and the result is a species that perhaps ought to be classified as something other than homo sapiens. (Particularly when you "augment" this genetic mutant with robotics and internal nano-machines designed to keep disease and physical obsolescence at bay.)
Mike Christie provided me with the earliest citations for this word.
Earliest Citation (adjective):
Robert Silverberg, Son of Man, 1971
post-traumatic job switcher