Abarim Publications' online Biblical Greek Dictionary
The noun ελαια (elaia) means olive and, as in English, this word denotes both an individual olive fruit and the whole olive tree. The word ελαιον (elaion) means olive oil. It isn't clear where these words come from (what the olive and olive oil meant to the ancients) but in Hebrew there's a strong suggestion towards being a first sapling, or the inaugurating signs of something new and fresh (see our article on the word זית, zayit, meaning olive).
In Latin there's the familiar word oleum for olive oil, but that word appears to be more akin oleo, meaning to smell (whether nice or not), whereas the Greek word ελαια (elaia) appears more associated with ελατη (elate), which denotes a kind of fir tree. This latter word also exists in Latin as elate, also denoting a fir tree, which is identical to the adverb elate, meaning loftily or proudly (hence our English word "elate").
This latter adverb in turn derives from the verb effero, meaning to bring or carry out or to bring forth. And that reminds of the Greek verb ελαυνω (elauno), meaning to impel or urge on.
In the Hebrew world, olive oil had been used to inaugurate kings, high priests and prophets — these were all known as "anointed one", or Messiah in Hebrew and Christ in Greek — but in the Greek world, olive oil was used for medicinal purposes (Mark 6:13, Luke 7:46), as fuel for lamps (Matthew 25:3), and as the base for a costly perfume called μυρον (muron).
Olive oil was produced on an industrial scale (Luke 16:6, James 3:12) and olive trees were everywhere. Paul used the image of the domesticated olive tree as symbol for Israel (Romans 11:17-24), but both Zechariah and John the Revelator enigmatically spoke of two olive trees that stand on the earth astride a lamp stand (Zechariah 4:3, Revelation 11:4). One of Jesus' favorite places was the Mount of Olives (Matthew 21:1, Mark 11:1, John 8:1) and His arrest occurred in Gethsemane, which means [Olive] Oil Press.
Other derivations are:
- Together with the adjective αγριος (agrios), meaning [uncultivated] field: the noun αγριελαιος (agrielaios), meaning wild or uncultivated olive tree. This word occurs only in Romans 11:17 and 11:24, where Paul compares gentile converts to branches of the wild olive tree which are grafted onto the trunk of the cultivated tree that is Israel.
- The noun ελαιων (elaion), denoting an olive grove or olive orchard. In the New Testament this word solely occurs as the name of what translations usually call Mount of Olives, or Olivet (see the link below).
- Together with the adjective καλος (kalos), mean good or rather godly: the adjective καλλιελαιος (kallielaios), denoting a cultivated olive tree (Romans 11:24 only), as opposed to αγριελαιος (agrielaios), the wild olive tree. The difference lies not in their tameness but in their functionality and purpose.