Terminology 

They are substantives derived from the French verb "tracer", which normally means "trace",[9] or "trail" (as in "he escaped without a trace").[10]

The "trail" bit, along with its explanation, doesn't seem to make much sense to me. The verb "tracer" is commonly used in French slang to denote fast movement. In the lexicon used in footnote [9], the most accurate definition would be II A 3: "Marcher vite", ("walking fast")and "filer" ("to go fast"). This is consistent with most of the synonyms of "tracer" that denote movement, such as "aller très vite"  or "courir"  .

It ties in with the fact that parkour is described as "moving around obstacles with speed and efficiency".

And finally, it also corresponds to the article about "traceur" on the French site: "tracer au sens familier de se déplacer à vive allure"  

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