The test was invented by a Greek physiologist named Georgios Papanicolaou. He was born on the island of Evia on the 13th May 1883. He attended the University of Munich and achieved his PhD in zoology in 1910. He then eloped with the woman he would spend the next 47 years of his life with, Andromache Mavroyeni, who went by Mary. The two returned to Greece in 1912, where Georgios served in the Balkan Wars. Following this, he and Mary immigrated to New York City in 1912.
Although initially playing violin in restaurants to pay the bills, Georgios quickly found work at Cornell Medical College slowly rising up the ranks. It was here that he made the observation that eventually led to the pap smear.
Papanicolaou was observing the ovulatory cycles of guinea pigs - but the lack of menstrual cycles made this difficult. Convinced that there must be some change in discharge over the month - just that it was too small to see, Papanicolaou used a paediatric nasal speculum and took slides, smears, of guniea pig vaginal discharge and was able to demonstrate changes. This proved of great value to researchers working with guniea pigs, rabbits, mice and other small animals as well as indirectly to the discovery of oestrogen and progesterone.
Papanicolaou had another goal in mind, however. He wanted to see if the results in guinea pigs could also be seen in humans. However, because he wasn't a clinician, he didn't have any access to patients. Except for one.
Every day, for the next 21 years, Mary patiently agreed to climb up onto an examination couch and have her vaginal fluid sampled and smeared. Slowly Papanicolaou began to establish that, just like guinea pigs, it certainly was possible to see a change throughout a monthly cycle.
After some time, however, Papanicolaou began to wish for more subjects to compare his results. So Mary asked some friends over for a party, and they too agreed to be sampled. Some weeks later, one of these women was diagnosed with cervical cancer. On hearing this news, Papanicolaou went back and examined her smear, taking it to be seen by another cytologist at Cornell. Together they discovered that cancerous cells were indeed visible on the smear.
This discovery allowed him further access and trials on patients. It confirmed that the pap smear could not only identify cancerous cells, but precancerous ones as well.
By the mid 1940s the technique was developed to the point where its widespread application was feasible. Papanicolaou began training people in the technique and eventually published a book on cytology in 1954.
He died of heart failure on Febuary 19, 1962, having only recently moved to Florida to direct a Cancer Institute which was post-humously renamed in his honour.
Thanks to his work, thousands and thousands of women are alive today.
However I think at least some of the credit should go to Mary Papanicolaou who worked as his assistant and for 21 years bravely submitted herself to a pap smear. She died in Miami in October 1982. Without her forbearance, Georgios Papanicolaou would have stalled before he started.