1650s, "covered with scurf," from scruff "dandruff, scurf" (late Old English variant of scurf) + -y (2). The generalized sense of "rough and dirty" is by 1871 ("Mark Twain"). Related: Scruffily; scruffiness.
late Old English scurf, "scaly or flaky matter forming on the surface of the skin," also "exfoliated epidermis," earlier sceorf, from Proto-Germanic *skurf- (source also of Old Norse skurfottr, Danish skurv, Swedish skorv, Middle Dutch scorf, schorf, Dutch schurft, Old High German scorf, German Schorf "scurf"), which probably is related to Old English sceorfan "to gnaw," scearfian "to cut into shreds" (from PIE *skerp-, from root *sker- (1) "to cut"). The form of the word likely is influenced by Scandinavian cognates. The scruff in scruffy is from a variant form.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).
<a href="https://www.etymonline.com/word/scruffy">Etymology of scruffy by etymonline</a>
Harper, D. (n.d.). Etymology of scruffy. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/scruffy