The surname Gill appears in the Roman Catholic parish records of Radun in the Lida deanery of the diocese of Wilno. Radun is now in western Belarus; earlier the area was within the boundaries of eastern Poland, earlier the Russian Empire, and earlier still, the Polish-Lithuanian Commonwealth. A Gill married into my Blaszko family in Radun parish in the late 1700s. I've seen this surname in the church registers through the late 1800s. It is likely of Scottish origin. Politics, commerce, aristocratic family alliances, and military endeavors brought a fair number of Scots to the Polish-Lithuanian Commonwealth in the 16th-18th centuries. A fair number of Poles/Lithuanians from Radun parish migrated to the Carbondale and Scrantona areas in the early 1900s. Gill may well be the correct surname. I would question what your immigrant's original first name was; "William" does not exist in Polish, but was often used by immigrants named Wicenty or Boleslaw, for example. Hope this helps!