One is Gershom, and one is Eliezer

Summary: What is bothering Ibn Ezra? I would guess that he is responding to Saadia Gaon, who makes much of the duplication.

Post: At the start of Yitro, we meet Moshe's two sons:

ג  וְאֵת, שְׁנֵי בָנֶיהָ:  אֲשֶׁר שֵׁם הָאֶחָד, גֵּרְשֹׁם--כִּי אָמַר, גֵּר הָיִיתִי בְּאֶרֶץ נָכְרִיָּה.	3 and her two sons; of whom the name of the one was Gershom; for he said: 'I have been a stranger in a strange land';
ד  וְשֵׁם הָאֶחָד, אֱלִיעֶזֶר--כִּי-אֱלֹהֵי אָבִי בְּעֶזְרִי, וַיַּצִּלֵנִי מֵחֶרֶב פַּרְעֹה.	4 and the name of the other was Eliezer: 'for the God of my father was my help, and delivered me from the sword of Pharaoh.'

Why should pasuk 4 begin veshem ha`eched. Shouldn't it be veshem hasheni? Obviously, this is an acceptable grammatical construction - one's name was X and one's name was Y - just as the opposite is a grammatical construction. But Ibn Ezra takes pains to spell it out, and that this is minhag leshon hakodesh:

[יח, ד]
ושם האחד -מנהג ל' הקדש לאמר פעמים ככה השני. ופעמים האחד. כמו: שם האחד בוצץ ושם האחד סנה. ותחסר מלת אמר אחר: כי אלהי אבי בעזרי. ואין כתוב: כי אמר אלהי אבי כי המלה שבה למעלה כי אמר: גר הייתי. כמו: כי הפרני אלהים. וכבר פירשתי למה קרא שם הקטן אליעזר.

He notes a parallel to I Shmuel 14:4, as an example:

ד  וּבֵין הַמַּעְבְּרוֹת, אֲשֶׁר בִּקֵּשׁ יוֹנָתָן לַעֲבֹר עַל-מַצַּב פְּלִשְׁתִּים--שֵׁן-הַסֶּלַע מֵהָעֵבֶר מִזֶּה, וְשֵׁן-הַסֶּלַע מֵהָעֵבֶר מִזֶּה; וְשֵׁם הָאֶחָד בּוֹצֵץ, וְשֵׁם הָאֶחָד סֶנֶּה.	4 And between the passes, by which Jonathan sought to go over unto the Philistines' garrison, there was a rocky crag on the one side, and a rocky crag on the other side; and the name of the one was Bozez, and the name of the other Seneh.
ה  הַשֵּׁן הָאֶחָד מָצוּק מִצָּפוֹן, מוּל מִכְמָשׂ; וְהָאֶחָד מִנֶּגֶב, מוּל גָּבַע.  {ס}	5 The one crag rose up on the north in front of Michmas, and the other on the south in front of Geba. {S}

Now, perhaps Ibn Ezra would take pains to make such a point clear, even though without him explaining this, it is hard to see where the confusion would be. Is he just noting interesting facts about the Hebrew language we can glean from this pasuk?

Sometimes, Ibn Ezra will explicitly cite context. But often, it pays to look to Rashi, or the midrash, and ask "what is bothering Ibn Ezra?" What would bother Ibn Ezra would not necessarily be something in the pasuk. Rather, he is responding to, and arguing with, some known position. Such that without learning Rashi or the midrashim, you would end up missing a lot from Ibn Ezra's intent.

And I would guess that this is one such instance. Here, I think he might be arguing with Saadia Gaon, who wrote:

ושם האחד אליעזר. והיה ראוי שיאמר ושם
השני וכתב הגאון ז״ל כי הטעם בזה לפי
שאליעזר הוא רומז לשמו של הקב״ה שנקרא
אחד שנאמר הלא אל אחד בראנו לכן לא רצה
להזכיר בו שני כי הוא אחד ואין שני ולכן עם
שונים אל יתערב:
( בספר צרור המור מרס"ג ז"ל )

This would then compel Ibn Ezra to respond as he did. And his argument is that it is a general pattern, and his prooftext is a pasuk that does not involve the shem haShem.