Over At Accelerating Future, Michael Anissimov has used Google Trends to do a quick analysis of how many people searched on the term "transhumanism" over the past five years.
The term grew out of futurism and science fiction that dealt with what humanity would look like in a world of cyborg implants and rampant biological engineering. In many ways cyberpunk told some of the first post human stories, with its plug heads and neuro-enhanced fighters.
What Anissimov found was that the term entered into people's searches just about three years ago, and then began showing up in news stories roughly one and a half years ago. Science fiction fans and futurists, however, have been using this term for over a decade. Most likely we're seeing a rise in the use of his term in mainstream media because biotechnology is catching up to science fiction. People really are turning into cyborgs, with smart implants – and we even have the technology to tissue engineer new organs for ourselves.
So it's no wonder that transhumanism has emerged from science fiction into everyday speech.