Yes, he was born in Vienna, the second biggest "Czech" city (the third is Chicago , or rather was, 100 years ago ), his father was Václav Černý, but written as Wácslaw Cžerný (with digraph Cž = modern Č) in those times (18th century).Czerny I think is the German form. I know a Czerny, composer that many pianist we suffered hahha
What about "Ponurý" as gloomy?
Ponurý (female form Ponurá), Temný (= dark, fem. Temná) and Temnota (fem. Temnotová ) would be a good choice, but in fact they are non-existent as last names.Temnota (darkness in singular) would make sense, it's perfectly Czech (though not a common surname) meaning just darkness.