Pihach

Theodorus is a Latinization of the Greek Θεοδωρος, which was written in Church Slavonic as Ѳєдѡръ. In Old Ukrainian this became Федор (Fedor), which in turn became Федір (Fedir), with the diminutive Федько (Fedko). This particular name presented a research problem for me when a civil-registry clerk could not find the record of my great-great-grandfather, Theodorus Pihach.

2007, John D. Pihach, “Names” (chapter 3, pages 21–42), in Ukrainian Genealogy: A Beginner’s Guide (paperback), Edmonton · Toronto: Canadian Institute of Ukrainian Studies Press, →ISBN, Given Names (pages 24–34), Origins (pages 24–25), page 25