from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
ROOT. That part of a tree or plant under ground from which it draws most of
its nourishment from the earth.
2. When the roots of a tree planted in one man's land extend into that
of another, this circumstance does not give the latter any right to the
tree, though such is the doctrine of the civil law; Dig. 41, 1, 7, 13; but
such person has a right to cut off the roots up to his line. Rolle's R. 394,
vide Tree.
3. In a figurative sense, the term root is used to signify the person
from whom one or more others are descended. Vide Descent; Per stirpes.