Английский Этимологический словарь - root (n.)

- "underground part of a plant," Late O.E. rot, from O.N. rot "root," from earlier *wrot, *vrot (with characteristic loss of -w- before -r-), from PIE *wrd-, thus related to O.E. wyrt "root, herb, plant" (see wort). The verb meaning "to pull up by the root" is from 15c.