Rezi is an abbreviated form (a nickname) for Terez or Tereza or Terezia (al= l variants of Teresa) in Hungarian, and may have been given to girls as Lyn= n Saul suggests in honour of the Empress Maria Theresa (in Hungarian Maria = Terezia).
I think Veronica Singer who suggested Reza was a man's name may have got it= mixed up with Geza which indeed is a man's name.
