Is it farther or further?
c.1600, from French contester "dispute, oppose," from Middle French, from Latin contestari (litem) "to call to witness, bring action," from com- "together" (see com-) + testari "to bear witness," from testis "a witness," (see testament). Calling witnesses as the first step in a legal combat. Related: Contestable; contested; contesting.
1640s, from contest (v.).