Carnaptious
Quarrelsome, irritable, crabbed in temper. The word for an old man who picks fights, a dog that snaps, a relative who can't be left alone in a room with strangers. Stronger than 'cranky', warmer than 'foul-tempered'.
Etymology
From an intensive prefix 'car-' or 'cur-' plus the Scots verb 'knap' (to bite), with the suffix '-ious'. The biting metaphor sits at the centre: a carnaptious person snaps. Recorded in print from 1879 onwards. The Cumberland dialect form 'knaptious' (= captious, quarrelsome) is cousin to it; both come from the same biting root.
In a sentence
a carnaptious auld bugger - Herald, 2000 (per DSL)
Historical notes
Carnaptious is one of the most useful Ulster Scots adjectives because it admits affection. The English alternatives - 'cantankerous', 'irritable', 'grumpy' - either flatten the personality or sound clinical. 'Carnaptious auld bugger' has been recorded across Scotland and Ulster for over a century and is heard equally about humans and dogs. The 2000 Herald sample is exactly the right register: a working description that doesn't entirely give up on the subject.
Alternate spellings
curnaptious · carnapshus · canaptious