This form of the letter s was standard in the past: https://en.wikipedia.org/wiki/Long_s https://en.wikipedia.org/wiki/Long_s Wikipedia has a long description

This form of the letter s was standard in the past: https://en.wikipedia.org/wiki/Long_s https://en.wikipedia.org/wiki/Long_s Wikipedia has a long description of the history and how it went out of use. It's actually not quite identical to the letter f (it's ſ rather than f) and is also the original of the integral sign in calculus.