Xenakis refereed the match between New Zealand and Bulgaria, where he made a call to send New Zealand Chaser Dennis Moon off after judging him to have caused a deliberate collision with a Bulgarian Chaser. This move drew the ire of New Zealand's manager Charlie Baverstock, and was deemed a crucial factor in Bulgaria's victory (Pm).
Georgios (English: George) comes from the Greek Γεωργιος (Georgios), deriving from the Greek γεωργος (georgos) "farmer, earthworker". This breaks down into γη (ge) "earth" and εργον (ergon) "work" (Behind the Name).
Xenakis may refer to Thomas Xenakis, a Greek gymnast who participated in the first Olympics of the modern era.
As Georgios is one of the most common first names in Greece, it is possible the character is Greek.
From the Web
Screenshots of the Daily Prophet's coverage of the 2014 Quidditch World Cup: http://imgur.com/a/AXutv