Stetsko/Stecko and any other transliteration/sounds like
variants of the original are just that, variants. The
only correct spelling of the surname is in its original language, using the Cyrillic Alphabet and it is СТЕЦКО.
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Steckovich/Steckowycz and any other transliteration/sounds like variants of the original are just that, variants. The
only correct spelling of the surname is in its original language, using the Cyrillic Alphabet and it is
СТЕЦКОВИЧ.
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Stay very flexible when researching these surnames!
You'll run into many variants, but check against birth dates or any other info you may have. Whenever possible use SOUNDEX.

PS> And yes it is possible that in some cases was shortened
from another name, but not always.