Time: Ancient research on real numbers likely "didn’t get improved upon until the age of Newton," says [John] Conway. by Olivia B. Waxman
'Sir Isaac Newton recorded 16 digits of pi in 1665, later admitting that he was "ashamed" of how long he had worked on the computations, as it meant that he had "no other business at the time," per the MAA.
'It was not until the 18th century — about two millennia after the significance of the number 3.14 was first calculated by Archimedes — that the name "pi" was first used to denote the number. In other words, the Greek letter used to represent the idea was not actually picked by the Ancient Greeks who discovered it.
'British mathematician William Jones came up with the Greek letter and symbol for the figure in 1706, and it was popularized by Swiss mathematician Leonhard Euler, Catherine the Great's mathematician, a few decades later.
'"Euler was a much better mathematician than the people who used [pi] before, and he wrote very good textbooks," says Conway. "He used it because the Greek letter Pi corresponds with the letter 'P'... and pi is about the perimeter of the circle."'