First remark: surnames ending in
-ski, -cki, -dzki are declined in Polish, that's why you'll have 2 versions (for men ending
-ski, -cki, -dzki; for women ending
-ska, -cka, -dzka).
I just found a site, but I don't know if it's reliable, someone more concerned about genealogy might be more helpful (because it's not my cup of tea)
Surname Gryszkowski - only 8 men + 6 women (Gryszkowska), all in Ełk region (NE Poland)
Surname Ryszkowski - 580 men + 610 women (Ryszkowska), in various regions of Poland (predominantly East, but almost 12% in Warsaw, which has about 5-6% of overall Polish population)
There are also 311 persons with the name Gry
czkowski (mostly in NE Poland) and, judging by the geographical distribution, it looks like Gry
szkowski is probably a misspelled version of Gry
czkowski, not Ry
szkowski (due to the historical and political circumstances mentioned by krysia in her post, I may add that the Germans during WWII also added to the mess, by writing incorrectly Polish names/surnames in their documents, many people had lost their Polish IDs during WWII and the German IDs were the only ones they had after the war, so if there were any mistakes they were transferred to Polish documents after WWII and some people never bothered to go to the court in order to bring back the correct spelling), but it apparently exists so it's hard to say who made the mistake in spelling and when (before 1918 - during partitions of Poland - or on Ellis Island in the 30's).
does this mean Ryszkowska (surname) OF Gryszkowska (Village/Town)?
The town/village name would rather be Ryszków / Gryszków (I haven't heard such names and haven't found any in Wikipedia, but it's not definitive, not every single of 35,000 Polish towns and villages is in Wiki), in the version Gry
czkowski, it may come from "gryczka" (a plant species)