Yanchuk is a Ukrainian name and it has been heavily americanized. I can't give the original to you in Ukrainian because they used the Cyrillic alphabet but I can give it to you in Polish, JANCZUK. Many Western Ukrainians lived in the historically Polish province of Galicia. It may well be that his Canadian family maintained the old country spellings. There were, and probably still are, Ukrainian minorities living in the wheat growing regions of Western Canada.