I was both surprised and tickled to discover that the damned thing had a Wikipedia entry. However, I’m not sure I accept what that entry says about the name:
The brand name Leibniz comes from the philosopher and mathematician Gottfried Wilhelm Leibniz. The only connection between man and biscuit is that Leibniz was one of the more famous residents of Hanover, where the Bahlsen company is based. At the time when the biscuit was first made there was a fashion of naming food products after historical celebrities (compare Mozartkugel).My guess is that there is a connection far more significant than playing catch-up with Wolfgang Amadeus Mozart. If the company is trying to catch up with anyone or anything, it would have to be Nabisco, who named a fig-filled cookie of their own after Isaac Newton and have recently expanded that particular brand to a wider variety of fillings. Anyone who is English will tell you that Newton invented differential and integral calculus or, as it is known more accurately, the calculus of infinitesimals. Europeans, on the other hand, disagree with opinions on the other side of the English Channel and attribute the invention to a German: Leibnitz. In other words a long-standing argument over a major achievement in mathematics is now being fought between cookie manufacturers. Anything Wikipedia may say about the Fig Newton being named for Newton, Massachusetts, where it was invented, is mere coincidence!