Alright, just digging up this thread to provide an update for other researchers...
The Czalauns originate from the Herzman/Protivin area in south Bohemia. They lived there for several generations as millers, mainly at the Beneshov Mill (Benessovsky Mlyn). Thanks to the archive of Trebon I could trace them down to the 1670s over there. Older source material doesnt seem to exist.