Green’s Dictionary of Slang

a despicable person.

[1825		C.M. Westmacott Eng. Spy I 82: Come fill the bowl with Bishop up, Clods, Fags, and Skugs, and Muttons. Note, Scug or Skug, a lower boy in the school, relating to sluggish].
1915		Wodehouse Psmith Journalist (1993) 258: We’ve been saying in the paper what an out-size in scugs the merchant must be who owns those tenements.
1944		S. Horler Lady with the Limp 147: Nothing would have pleased him more than to try to knock this scug’s block off.
1956		N. Mitford Noblesse Oblige (1980) 87: I mean slang in the sense of a tribal patois (e.g. scug, an inconsiderable or unworthy person).
1965		J.P. Carstairs Concrete Kimono 177: I always said you were a scug at Eton and scug you still are.