Genealogy / THE MEANING AND RESEARCH OF MY POLISH LAST NAME, SURNAME? [4500]

Using some recently digitized records I was able to add a few more generations to my grandfather's Polish ancestry. Moving into the 18th century records I made a curious discovery; the family name changed. Suddenly the name I had been researching, Turkiewicz, was no longer appearing in the birth/marriage/death records. However, a new name appeared that didn't exist in the 19th century records for the village, Turkiniak. Comparing the families bearing the two surnames it is evident they are the same people. So what happened?

The Turkiewicz name appears in neighboring parishes and I find no other instances where it was changed. Was this something done by the priest? Did Bazyli just decide one day that he didn't want to be "the little Turk" anymore and declared before the church congregation that from now on he would be "son of the Turk"? His brother, Marcin, must have made the same declaration since he was born a Turkiniak and died a Turkiewicz as well.

This has stirred up a lot of questions that will probably never be answered without resurrecting some dead relatives. Has anybody experienced a similar change in surnames?