Iacobus

Iacobus is the true Latin form of James which is another variation of the name Jacob. Sanctus Iacobus in Latin is Saint James in English while Jacob is simply translated as Iacob in latin. The late form Iacomus is only a cognate of Iacobus, with the same meaning and the same etymology. It's a fact that Jacob and James are not separate names but the same name; around the world, in the most part of languages, James doesn't exist but there is only Jacob used for both names. It's a mistake considering the two as different names.