"prickly seed vessel of some plants," c. 1300, burre, from a Scandinavian source (compare Danish borre, Swedish hard-borre, Old Norse burst "bristle"), from PIE *bhars- (see bristle (n.)). Transferred 1610s to "rough edge on metal," which might be the source of the sense "rough sound of the letter -r-" (see burr). Also the name given to various tools and appliances.
name for various tall, coarse weeds or herbs, Old English docce, from Proto-Germanic *dokkon (source also of Middle Dutch docke-, German Docken-, Old Danish dokka), akin to Middle High German tocke "bundle, tuft," and ultimately to the noun source of dock (v.1).
<a href="https://www.etymonline.com/word/burdock">Etymology of burdock by etymonline</a>
Harper, D. (n.d.). Etymology of burdock. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/burdock