It is not Spanish but Latin, and it is not even in the nominative Iacobus so I suppose it will be a fragment of another longer text (surely Liber Sancti Iacobi). If Iacobi is a genitive, it translates as "of Jacobo" although in Spanish "of Santiago" is preferred, which by the evolution of the name can be equivalent, as Yaco, Yago or Tiago.
