Sulky, bad-tempered, morose, or out of sorts; in a bad mood and inclined to be disagreeable.
From Scottish/Northern English dialect, possibly related to 'dour' (meaning stern or severe). The '-y' suffix converts the root into an adjective. The exact origin is uncertain, but it's well-documented in Scottish English from at least the 18th century.
Scottish English gave English speakers 'dour,' but it also gave us 'dorty' for the emotional version—if you're dour, you look stern, but if you're dorty, you're actively being difficult about your bad mood.
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