Did Devorah exist?

What was the Tomar Devorah?

וַיַּעֲבֹר אַבְרָם, בָּאָרֶץ, עַד מְקוֹם שְׁכֶם, עַד אֵלוֹן מוֹרֶה; וְהַכְּנַעֲנִי, אָז בָּאָרֶץ.

6 And Abram passed through the land unto the place of Shechem, unto the [oak] of Moreh. And the Canaanite was then in the land.

בְּאֶרֶץ הַכְּנַעֲנִי, הַיֹּשֵׁב בָּעֲרָבָה--מוּל, הַגִּלְגָּל, אֵצֶל, אֵלוֹנֵי מֹרֶה.

30 Are they not beyond the Jordan, behind the way of the going down of the sun, in the land of the Canaanites that dwell in the Arabah, over against Gilgal, beside the [oaks] of Moreh?

Moreh means teacher, so the elon moreh might refer or somehow relate to a  teacher who once upon a time sat under an oak tree. It may also relate to diviners, or a divenly inspired teacher, who sat under an oak tree.
Thus:

לז  וַיֹּסֶף עוֹד גַּעַל, לְדַבֵּר, וַיֹּאמֶר, הִנֵּה-עָם יוֹרְדִים מֵעִם טַבּוּר הָאָרֶץ; וְרֹאשׁ-אֶחָד בָּא, מִדֶּרֶךְ אֵלוֹן מְעוֹנְנִים.

37 And Gaal spoke again and said: 'See, there come people down by the middle of the land, and one company cometh by the way of Elon-meonenim.

Me'onenim means "of the diviners", so the elon me'onimin conceivably refers to an oak treek assoicated with prophets or soothsayers.

On this basis, Wolfgang Richter says Devorah's tree, the tomar devorah under which the prophetess held court, was an oak tree, not a palm tree as is widely assumed. Moreover, he suggests that the tree mentioned in Genesis 35:

וַתָּמָת דְּבֹרָה מֵינֶקֶת רִבְקָה, וַתִּקָּבֵר מִתַּחַת לְבֵית-אֵל תַּחַת הָאַלּוֹן; וַיִּקְרָא שְׁמוֹ, אַלּוֹן בָּכוּת.  {פ}

8 And Deborah Rebekah's nurse died, and she was buried below Beth-el under the oak; and the name of it was called Allon-bacuth.

.. is the very same oak tree. This, he suggests, explains the cameo appearence of Devorah, the previously unnamed nurse. It's an eitological tale, he argues,  created to tell us how what must have been a famous oak first recived its name.

Richter goes on to suggest that the tree mentioned in Samual 10

וְחָלַפְתָּ מִשָּׁם וָהָלְאָה, וּבָאתָ עַד-אֵלוֹן תָּבוֹר, וּמְצָאוּךָ שָּׁם שְׁלֹשָׁה אֲנָשִׁים, עֹלִים אֶל-הָאֱלֹהִים בֵּית-אֵל; אֶחָד נֹשֵׂא שְׁלֹשָׁה גְדָיִים, וְאֶחָד נֹשֵׂא שְׁלֹשֶׁת כִּכְּרוֹת לֶחֶם, וְאֶחָד, נֹשֵׂא נֵבֶל-יָיִן.

3 Then shalt thou go on forward from thence, and thou shalt come to the terebinth of Tabor, and there shall meet thee there three men going up to God to Beth-el, one carrying three kids, and another carrying three loaves of bread, and another carrying a bottle of wine.

is the same tree, arguing that tabor is a scribal error, and that devorah was the original text. (In Hebrew they are close but, honestly, not that close)

James Kugel further deveolps ths idea, arguing that the proper name Devorah, when used to refer to the tree, is actually the generic word daborah which means "female speaker."  Perhaps once upon a time, female oracles were associated with that particular tree or with a tree of the same species. Over time, via synechede, the tree itself became known as the Tomar daborah. 

Did Devorah exist?

Kugel seems to agree with the theory that the poetic parts of the Torah are earlier than the narrative sections, and he has argued that the disagreements between the narrative sections and the poetic sections can be chalked up to errors in understanding. For example, the song of Devorah tells us that Sisreh fell at Yael's feet, but in the narrative portion he is prone and sleeping when he is killed. Kugel says this contradiction was introduced because the historian who wrote the prose section misunderstood the poetry. 

יָדָהּ לַיָּתֵד תִּשְׁלַחְנָה,  {ס}  וִימִינָהּ  {ר}  לְהַלְמוּת עֲמֵלִים;  {ס}  וְהָלְמָה סִיסְרָא מָחֲקָה  {ר}  רֹאשׁוֹ,  {ס}  וּמָחֲצָה וְחָלְפָה רַקָּתוֹ.  {ס}

26 Her hand she put to the tent-pin, her right hand to the workmen's hammer; and with the hammer she smote Sisera, she smote through his head, yea, she shattered and pierced his temple.

According to Kugel, the verse is better translated: "She put her hand to a stick, her right hand to a workman's club." He admits the intent is ambiguous - Did Yael perform two seperate actions, or is the poet simply describing the same action in two different ways, using a "replacement strategy" often seen in biblical poetry? But on the basis of the context, Kugel argues that the meaning is closer to "she took a stick, nay a mighty club". After all, the song says Sisreh was standing when he was hit, and that he fell at Yael's feet. Its hard to imagine Yael having the opportunity to approach a concious Sisreh with a tent peg in one hand and a mallet in the other. Its more likely that she came up behind him and smashed him on the side of the head with stick.

According to Kugel the historian who used the song as a source for his narrative misunderstood this (and perhaps didn't like the idea of a woman acting so brashly) To allow for the tent peg on one hand and a mallet in the other, he depicts Sisreh as sleeping and allows Yael to attack him in a fasion that is far more demure. 

Kugel goes on to say that the creation of the historical Devorah may have been the result of a similar error. One of the song's mentions of Devorah looks like this:

עוּרִי עוּרִי דְּבוֹרָה,  {ס}  עוּרִי  {ר}  עוּרִי דַּבְּרִי-שִׁיר;  {ס}  קוּם בָּרָק וּשְׁבֵה שֶׁבְיְךָ, בֶּן-  {ר}  אֲבִינֹעַם.  {ס}

12 Awake, awake, Deborah; awake, awake, utter a song; arise, Barak, and lead thy captivity captive, thou son of Abinoam.

According to Kugel, the reference originally may have been to an anonymous female prophet, a daborah. Misunderstanding this (and perhaps having some theological need to connect Barak's victory to a prophet) the historian who wrote Judges 4 invented a character called Deborah.

Additional support for this theory is provided by the third-person mention of Deborah earlier in the song:

חָדְלוּ פְרָזוֹן בְּיִשְׂרָאֵל,  {ר}  חָדֵלּוּ--  {ס}  עַד שַׁקַּמְתִּי דְּבוֹרָה, שַׁקַּמְתִּי אֵם בְּיִשְׂרָאֵל.  {ס}

7 The rulers ceased in Israel, they ceased, until that thou didst arise, Deborah, that thou didst arise a mother in Israel.

Kugel and others read this: "Until you arose, daborah." Or, until you delivered the prophecy, things were going poorly for Israel. He notes that when read this way, daborah is merely a generic word, and not a proper name.