"having a rough, irregular, or ragged appearance," 1831, from scrag + -ly (1); also compare scraggy (13c.). Scraggling in the same sense is by 1722; Milton used scragged (attested from 1590s).
Entries linking to scraggly
scrag n.
1540s, "lean person or animal, a raw-bones;" perhaps from a Scandinavian source (compare Norwegian skragg "a lean person;" dialectal Swedish skraka "a great, dry tree; a long, lean man," skragge "old and torn thing," Danish skrog "hull of a ship; carcass," Icelandic skröggr, a nickname of the fox); perhaps from the same source as shrink.
By 1640s as "lean end of a cut of meat," hence "neck" (18c.) and thence a range of slang verbal terms for "to strangle, to hang; to kill" in 19c.-20c.
-ly 1
suffix forming adjectives from nouns and meaning "having qualities of, of the form or nature of" (manly, lordly), "appropriate to, fitting, suited to" (bodily, earthly, daily); irregularly descended from Old English -lic, from Proto-Germanic *-liko- (Old Frisian -lik, Dutch -lijk, Old High German -lih, German -lich, Old Norse -ligr), related to *likom- "appearance, form" (Old English lich "corpse, body;" see lich, which is a cognate; see also like (adj.), with which it is identical).