"Matej" is written with a wedge above E - in Czech it's quite a difference between E and Ě, it sometimes changes the meaning. Sorry if you're not able to write it correctly because of the coding of the site.
This is also the Croatian form of Matthew. Short forms include: Mate, Mato, Matko. These are also normally associated with the name Matija. [noted -ed]
It is a mistake to connect Matej (Slovak) and Matìj (Czech) with Matthew (the Evangelist) instead of Matthias (the Apostle replacing Judas). Matthew is Matouš (Czech) or Matúš (Slovak). [noted -ed]