Green’s Dictionary of Slang

scag n.³

(US campus/black) an unattractive female.

1964		see skag n. (1)
1966		R. Stone Hall of Mirrors (1987) 55: A crew of ageing scags were entertaining three drunk [...] banana-handlers.
1974		J. Lahr Hot to Trot 222: She’s a scag.
1978		S. King Stand (1990) 668: The others [...] had lumped her in with other girls as a ‘pig’ or a ‘scag’.
		ng 7: scag – a female usually not attractive or mean.
1991		D. Jenkins You Gotta Play Hurt 316: ‘Honey, T.J.’s a celebrity. [...] He’s got all kinds of scags after his body’ .
1996		Eble Campus Sl. Mar.

In derivatives

scaggy (adj.)

unattractive.

1969		S.A. Williams Tell Martha Not to Moan in Chametzky Black and White 267: If Time got to give a hard way to go it ain’t gon be for no scaggy fay babe.
1981		J. Maynard Baby Love 55: But there were those kind of scaggy twins that really got off on it.
1999		C. Holden Four Corners of Night 382: The two scaggy girls sitting on the ratty furniture stare at me with opened mouths.
2003		J. Patterson Cat and Mouse 96: He thought about doing her, boffing the scaggy hotel maid, but he figured that wasn’t such a good idea.
2005		C. Kinder Last Mountain Dancer 312: He hadn’t mentioned it earlier because they were old, trashy, scaggy girls.