OIL TREE (עֵ֣ץ שָׁ֑מֶן). Mentioned only once in the OT—“I will plant in the wilderness...the oil tree” (Isa. 41:19 KJV).
The same word is used here as in Isaiah 61:3, “to give unto them...the oil of joy for mourning.”
The word used עֵ֣ץ שָׁ֑מֶן or עֲלֵי־עֵ֣ץ שֶׁ֔מֶן is the actual word used in Nehemiah 8:15 tr. “pine branches”—prob. really Oleaster branches, i.e. the Elaeagnus angustifolia.
Though some experts have said that the oil tree is really Balanites aegyptiaca, a tree which can indeed produce a kind of oil, the writer cannot find any record of this species of tree growing in the Jordan Valley. On the other hand, the Jordanians state that Zackum, known as the Balanites tree, does give medicinal oil of value.
This word has been tr. “olivewood” (1 Kings 6:23, 31, 32 and 33). The margin in some Bibles actually says “oily trees of oil.” For instance, the reading in 1 Kings 6:31—“He made doors of olivewood”—could be “He made the door of oily trees of oil.”
The olives themselves, of course, produce olive oil, or, as in Great Britain, “salad oil.” In the ASV, the Isaiah reference is “oil-tree,” while the pine in Nehemiah is “wild olive.”
International Standard Bible Encyclopedia (1915)
tre (’ets shemen (Isa 41:19), margin "oleaster," in Ne 8:15, translated "wild olive," the King James Version "pine"; ’atse shemen, in 1Ki 6:23,31,32, translated "olive wood"): The name "oleaster" used to be applied to the wild olive, but now belongs to quite another plant, the silver-berry, Eleagnus hortensis (Natural Order Elaeagnaceae), known in Arabic as Zeizafan. It is a pretty shrub with sweet-smelling white flowers and silver-grey-green leaves. It is difficult to see how all the three references can apply to this tree; it will suit the first two, but this small shrub would never supply wood for carpentry work such as that mentioned in 1 Kings, hence, the translation "olive wood." On the other hand, in the reference in Ne 8:15, olive branches are mentioned just before, so the translation "wild olive" (the difference being too slight) is improbable. Post suggests the translation of ’ets shemen by PINE (which see), which if accepted would suit all the requirements.