From The Washington Post:
How suggestively their names intertwined from the start: Masters, with its echoes of bondage and onanism, and Johnson, that venerable euphemism for penis. If they hadn't been the most famous sexologists of their day, they might have opened an S&M club in Tribeca. Gini, with her purring smile, would have greeted the customers; Bill would have stayed in the back room, testing the hoists and chains. Which was only a couple of degrees removed from what they did in real life. Their partnership began in St. Louis in the mid-1950s, when William Masters, an ob-gyn and fertility specialist at Washington University, decided to launch a scientific inquiry into human sexuality. Unlike his predecessor, Alfred Kinsey, Masters proposed something far more immersive than questionnaires: direct observation of the body's procreative functions, with each pulse and quiver painstakingly recorded.
He began in a small way by spying on prostitutes (conscripted with the local vice squad's help and the Catholic archbishop's blessing). When one of his subjects suggested he find a female partner, Masters settled on an unlikely candidate: an unemployed, twice-divorced mother with two small kids and no degree. Initially hired as Masters's secretary, Virginia Johnson quickly proved her worth in the lab, efficiently gathering personal histories and sounding the notes of empathy that were absent from Masters's cool register.