Easton's Bible Dictionary
The "olive-tree, wild by nature" (Romans 11:24 ), is the shoot or cutting of the good olive-tree which, left ungrafted, grows up to be a "wild olive." In Romans 11:17 Paul refers to the practice of grafting shoots of the wild olive into a "good" olive which has become unfruitful. By such a process the sap of the good olive, by pervading the branch which is "graffed in," makes it a good branch, bearing good olives. Thus the Gentiles, being a "wild olive," but now "graffed in," yield fruit, but only through the sap of the tree into which they have been graffed. This is a process "contrary to nature" (11:24).
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain.
Easton, Matthew George. Entry for 'Olive-Tree'. Easton's Bible Dictionary. https://www.studylight.org/dictionaries/eng/ebd/o/olive-tree.html. 1897.