Isaac Newton and Gottfried Leibniz invented calculus in the mid-seventeenth century. Newton gave it the very tedious name "the science of fluents and fluxions" and Leibniz was the one who gave it its modern name- it's not surprising that Newton's name didn't stick. Leibniz borrowed the word from Latin, where it referred to "a pebble used for counting", with a connection of solving mathematical problems. Because many of these pebbles were made out of limestone, we can further trace this back to the Latin word for "limestone", calx (making it related to words as diverse as causeway, recalcitrant, calcium, and chalk). This is from Greek khalix, also meaning "pebble" but nothing to do with counting this time. Origins of this are surprisingly obscure. It might be from a Proto-Indo-European word meaning "to break up", or it might have a non-IE Pre-Greek origin. Hopefully future resources will shed some light on that. As for now, it's all Greek to us.
Adam Aleksic, a leading contender for valedictorian of his high school, is a 211-month-old boy with disturbing interests in etymology, vexillology, geography, and law. Adam would like to one day visit Tajikistan and probably isn't spying for the Kyrgyz government.
The Etymology Nerd