'Root' in the Bible

Even now the axe [of God’s judgment] is swinging toward the root of the trees; so every tree that does not produce good fruit is being cut down and thrown into the fire.”

Those on the rocky soil are the people who, when they hear, receive and welcome the word with joy; but these have no firmly grounded root. They believe for a while, and in time of trial and temptation they fall away [from Me and abandon their faith].