[Surname] Re: Sulo or Shulo surname; origin Slovak or Czech?
From my research, the original forms of these surnames are Šulo and Dzurenda respectively and both are primarily Slovak.
I couldn't find any concrete etymological information for Šulo, but I suspect that it may be cognate to Old Polish 'szuło' or Russian шуло (shulo), both meaning "pole; post" possibly denoting a fence builder or someone who was tall and slender. As for Dzurenda, it is related to the more common Dzurinda which comes from Jakub (believe it or not), which is the Slovak form of Jacob.