Where does “де́що” come from?

де́що (Ukrainian) comes from Serbo-Croatian де-, from Latin dē-, from Latin dē, from Latin post, from Latin poste, from Proto-Italic posti, from Proto-Indo-European pósti, from Proto-Indo-European pós — afterwards, post; by, at.

де́що (Ukrainian): something or stuff, often insignificant, unimportant, or unknown. Can also signify something intentionally undisclosed in some situations