Hi,
Here you'll see 28 Arretz' currently in www.arch.be
http://search.arch.be/nl/zoeken-naar-personen/zoekresultaat/q/persoon_achternaam_t_0/arretz/q/zoekwijze/s?M=0&V=0&O=0&persoon_0_periode_soort=geboorte&persoon_0_periode_geen=0&sort=akte_datum&direction=asc
The oldest one on that list is Guilielmus Arretz, born 03 June 1824 in Ratingen, Germany, parents Joannes Arretz and Margareta "Hältgen"
One of the first results for "arretz ratingen" in Google is:
I hope that gets you started, good luck!