'Dark' has no clear origin outside West Germanic — its etymology is literally as obscure as its meaning.
The absence of light; a place or time characterized by the absence of light.
From Old English 'deorc' (dark, without light, obscure, gloomy), from Proto-Germanic *derkaz (dark, hidden), possibly from PIE *dʰerg- (to darken, to conceal, to hide). The word is peculiarly restricted to the West Germanic languages — it has no cognates in North Germanic (Scandinavian) or in Gothic, let alone in other Indo-European branches. This isolation makes 'dark' one
Unlike most basic English words, 'dark' has no known cognates outside the West Germanic languages — no Old Norse, no Gothic, no Latin, no Greek equivalent from the same root. It appears to be a Germanic innovation or a word borrowed from an unknown pre-Germanic substrate language. For such a fundamental concept, its origin is remarkably obscure — which is, etymologically, quite fitting.