From EL GIBBOR: http://www.angelfire.com/space/thegospeltruth/trinity/verses/Isaiah9_6-1.html

The two words translated by Trinitarians as “Mighty God” at Isaiah 9:6 are the words “EL GIBBOR” where they translate the word GIBBOR as “Mighty.” In the very next chapter of Ezekiel (32:21), the words el gibbor are used in plural form of earthly men. Here again the term is a reference to men and Trinitarians are quite careful to make sure they do not translate the passage as “Mighty Gods will say” but have instead something like “the leaders will say” or “the strong among the mighty ones” or some similar concoction. The English words which translate Hebrew EL are underlined below in the following translations.

• The strong among the mighty shall speak to him. KJV
• The strong among the mighty ones shall speak of him. NASB
• The mighty chiefs shall speak of them. RSV
• The strong among the mighty shall speak to him. ASV
• The mighty chiefs shall speak of them. ESV
• the mighty leaders will say. NIV
• the mighty warriors shall speak. NAB

Carefully observe how Trinitarian scholars translated the same words differently in Ezekiel 21 than they did at Isaiah 9:6. Also compare the following:

• Isaiah 9:6 – Wonderful, Counsellor, MIGHTY GOD, Eternal Father.
• Isaiah 9:6 – Wonderful, Counsellor, EL GIBBOR, Eternal Father.
• Ezekiel 32:21 – EL GIBBOR shall speak to/of him.
• Ezekiel 32:21 – THE MIGHTY LEADERS shall speak to/of him.

Note the difference in translation of the same two Hebrew words:

• Ezekiel 32:21 – THE MIGHTY LEADERS shall speak to/of him.
• Isaiah 9:6 – Wonderful, Counsellor, MIGHTY GOD, Eternal Father.

The fact that Trinitarians translate the Hebrew word el to be convenient to their doctrine illustrates their so-called evidence is not evidence at all but a personal desire to promote their doctrine by dishonest means wherever they think they can get away with it.

Addendum

Edwin Louis Cole, Courage, Winning Life’s Toughest Battles (Tulsa: Harrison House: 1991), p. 159:

“The word designated for the expected Messiah in Isaiah 9:6 is el gibbor (from the root word, geber). It is usually translated ‘Mighty God,’ but more exactly it is ‘Powerful Champion’ or ‘Godly Hero.’”

John Schoenhieit, The Sower (bi-monthly magazine) Mar/Apr 2006, Spirit & Truth Fellowship International:

“The word gibbor means strong or mighty, and refers to someone who is bold or audacious, strong or valiant. The phrase ‘el gibbor’ is used in the plural in Ezekiel 32:21 (ESV, NRSV, RSV), where it is translated ‘mighty chiefs,’ ‘mighty leaders (NIV), ‘strong among the mighty’ (KJV), ‘mightiest heroes’ (NJB), and ‘mighty warriors’ (Moffatt). Given that generally an ‘el’ is a ruler in some sense, and gibbor means strong or mighty, ‘Mighty Ruler’ would be a good choice for the translation of Isaiah 9:6, and that is exactly what the Jews were looking for in their Messiah.”

Driver & Briggs, Hebrew & English Lexicon of the OT, 1995, p. 42:

[el gibbor] “mighty hero or divine hero, as reflecting the divine majesty.”

NET Bible:

The title portrays the king as God’s representative on the battlefield, whom God empowers in a supernatural way (see J. H. Hayes & S. A. Irvine, Isaiah, 181-82…this sense seems more likely in the original context of the prophecy. [From the NT] we might in retrospect interpret this title as indicating the coming king’s deity, but it is unlikely that Isaiah or his audience would have understood the title in such a bold way. Ps 45:6 addresses the Davidic king as “God” because he ruled & fought as God’s representative on earth….When the king’s enemies oppose him on the battlefield, they are, as it were, fighting against God himself.

Cambridge Bible for Schools & Colleges:

The mighty God (’êl Gibbôr) either “God-like Hero” or Hero-God…These two titles ascribe to the Messiah the two fundamental virtues of a ruler, wisdom and strength (cf. ch. Isaiah 11:2), both in superhuman measure. The predicate of divinity (like that of eternity in the next name) is not to be understood in the absolute metaphysical sense; it means that the divine energy works through him and is displayed in his rule (cf. Isaiah 11:2 ff.; Mi. Isaiah 5:4; Zechariah 12:8).

Kegan, The God of Jesus, p 477:

The name “el gibbor” given to the Messiah here should be understood in light of other Hebrew names such as Gabriel which uses the same Hebrew characters as “el gibbor.” The name no more proves that the angel Gabriel is God than Elijah’s name (“my God Yahweh”).  The name “el gibbor” denotes the Messiah’s authority, strength and excellence, and has nothing to do with him actually being the one true God of Israel.  Again, such an interpretation would have been met with wide eyes by both the ancient Israelites and Jesus’ first-century Jewish Apostles.

In the Bible, El is often combined in proper names: Isra-El; Shmu-El (Samuel); El-ijah; Immanu-El; Jo-El; Dani-El; Beth-El. It’s also found in compounds: El Shaddai, El Elyon, El Roi, El Olam.