I was recently reading some historical records wherein a lady was mentioned, Olga Malar (née Cuch), born in "Napodiwka," Poland, in 1922. She was said to be the daughter of Xelefon Cuch and Jewdokia Romaniuk.
Every individual name on the record can be cross-referenced elsewhere, apart from the birthplace, and father's given name (Xelefon). Both are possibly misspellings, but of what?
Online, there are barely any concrete results for a search of Xelefon, or even possible permutations like Kselefon, Helefon or Chelefon.
It seems particularly unusual for the letter x to appear in Polish. It is not part of the standard alphabet, though it may appear in calques. However, even then, x is often substituted for ks, for example.
EDIT: No official answers by 2020.