'Olive tree' in the Bible

But if some of the branches were broken off, and you [Gentiles], being like a wild olive shoot, were grafted in among them to share with them the rich root of the olive tree,

For if you were cut off from what is by nature a wild olive tree, and against nature were grafted into a cultivated olive tree, how much easier will it be to graft these who are the natural branches back into [the original parent stock of] their own olive tree?