1 a policeman 20-.
2 a bad man 20-.
3 a cheat 20-. etymology: Cant shan ‘bad’ + Scots cowl ‘a man’; sense 1 attested by JS; senses 1, 2 and 3 attested by BS in TDITA but compare callo gaugie and kallo note:
Canadian Paul Pope (2013) cites this shan cowl as ‘a bad man’ and ‘a black man’.