1911 Encyclopædia Britannica/Bur
BUR, or Burr (apparently the same word as Danish borre, burdock, cf. Swed. kard-boore), a prickly fruit or head of fruits, as of the burdock. In the sense of a woody outgrowth on the trunk of a tree, or “gnaur,” the effect of a crowded bud-development, the word is probably adapted from the Fr. bourre, a vine-bud.