Why is the displacement symbol "s"?

(Created prior to 1993)
  
Question: I have wondered for some time why the symbol "s" is commonly used 
to represent the quantity "displacement."
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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.

Sam Bowen
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