c. 1300, "to perform as an acrobat," also "to fall down," perhaps from a frequentative form of Old English tumbian "dance about, tumble, leap." This is of unknown origin but apparently related to Middle Low German tummelen "to turn, dance," Dutch tuimelen "to tumble," Old High German tumon, German taumeln "to turn, reel." Transitive sense from late 14c. Related: Tumbled; tumbling.
"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.
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Definitions of tumbleweed from WordNet
any plant that breaks away from its roots in autumn and is driven by the wind as a light rolling mass;
prickly bushy Eurasian plant; a troublesome weed in central and western United States;