I have wondered for some time why the symbol "s" is commonly used
to represent the quantity "displacement."
I have looked around and cannot find out where this started. It
might be so simple as the fact that s is close to v and t which both appear in
distance formulas. Lots of expressions have letters from similar parts of the
alphabet as a way of recognizing copying errors. It may also be German. I
will be look into this a little bit later. I note that in the math literature
when the length of a line is mentioned it is often called s. Again I do not
know of any reason. Many of these conventions are very old and often limited
to a particular audience.