pronoun
Dated, derogatory, or familiar pronoun for a third person. Often used with contempt or rough familiarity, similar to 'that fellow' or 'that guy' in older or stylized speech.
きゃつは何を考えているのかさっぱりわからん。
I have no idea what that guy is thinking.
きゃつの言うことなど気にするな。
Don't mind what he says.
Derived from 彼 (ka) + 奴 (yatsu), with sound change. The exact historical development is uncertain, but it is an old colloquial form.