The Collaborative International Dictionary of English v.0.48:

Prochein \Pro"chein\, a. [F. prochain, fr. L. (assumed)
   proximanus, fr. proximus.]
   Next; nearest.
   [1913 Webster]

   Prochein ami or Prochein amy(Law), the next friend. See
      under Next.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

PROCHEIN. Next. This word is frequently used in composition; as, prochein
amy, prochein cousin, and the like. Co. Lit. 10.