calculate [LME] The Latin word calculus meant ‘a small pebble’, specifically one used on an *abacus. This is the base of Latin calculare ‘to count’, from which calculate comes. Calculator [LME] first meant a person who calculates, just as a *computer was a person who computes. Calculus has become an English word in its own right, as the name of a branch of mathematics, since the late 17th century.