Jesu Christu

In the book I'm reading, The 52, by Mario Reading, a Gypsy uses the expletive Jesu Christu. I can't figure out what language that is. I'm a reading a German translation, but the German would be Jesus Christus. Jesu points to the Latin form in the vocative, but then the entire expression should be Jesu Christe (Jesus is a fourth declension and Christus a second declension noun), I wonder if it's Romani, since the story revolves around Roma and is uttered by Alexi, a Gypsy youngster.