ragweed n.

of clothing or garments, "rough, shaggy," c. 1300 (late 12c. in surnames), past-participle adjective as though from a verb form of rag (n.1). Compare Latin pannosus "ragged, wrinkly," from pannus "piece of cloth." But ragged might reflect a broader, older meaning of the noun rag (n.1), perhaps from or reinforced by Old Norse raggaðr "shaggy," via Old English raggig "shaggy, bristly, rough" (which, Barnhart writes, "was almost surely developed from Scandinavian").

Of persons, "wearing tattered clothes," late 14c. From late 14c. of plants or leaves, "serrated." To run (someone) ragged is from 1915. Related: Raggedly; raggedness.

"plant not valued for use or beauty," Old English weod, uueod "grass, herb, weed," from Proto-Germanic *weud- (source also of Old Saxon wiod, East Frisian wiud), of unknown origin. Also applied to trees that grow abundantly. Meaning "tobacco" is from c. 1600; that of "marijuana" is from 1920s. The chemical weed-killer is attested by 1885.