Actually when contacting relatives in both Poland and Slovakia, the name over there is actually spelled Ewancik, ofor those family members on the Slovakian side and on the Polish side, the family Polonized the name into Jannusik after WWII as being Carpatho-Rusyn, or Lemko, this kept them from being repatriated into the Ukrainian Republic under Stalin's repatriation of Ukrainians. I do not know why, but the family name is actually spelled with the "E" and pronounced as the name IVAN would be in any SLavik language, as you noted. Rusyn is an oddball language among the Slavik languages and there are numerous arguments as to whether it is related to Ukrainian or Slovak, or actually constituted its own separate language rather thanb being a dialect of these two mentioned. My own name Nicholas is spelled Mikolaj, so go figure.