When Dr. Ilana Sasson of Teaneck was growing up in Israel, the child of Iraqi immigrants, she was embarrassed by the Arabic her parents would speak at home.

“I wanted people to speak Hebrew,” she said. “Kids who had Yiddish in their house felt the same. It was more so for those of us coming from the Islamic world, since Arabic was identified as the language of the enemy.”

Her childhood self would be quite surprised, therefore, that Dr. Sasson wrote a dissertation on a Judeo-Arabic translation and commentary on the biblical book of Proverbs. A revised version of the dissertation was published this summer by Brill Publishers as “The Arabic Translation and Commentary of Yefet ben Eli on the Book of Proverbs.”

Yefet ben Eli lived in the last decades of the first millennium. He was a native of Basra in present-day Iraq, the same city Dr. Sasson’s parents came from a thousand years later. Like them, he moved to Israel. Unlike them, he was a Karaite — rejecting the authority of the Talmud and insisting on the right, and importance, of interpreting the Bible independently. His was the central Karaite translation of the Tanach. It was popular among Karaite Jews. At the same time, the Arabic commentary of Saadya Gaon, a staunch opponent of the Karaites from earlier in the 10th century, was becoming popular among rabbinic Jews.

“There are many copies of his books,” Dr. Sasson said. “If you go to the institute of microfilmed Hebrew manuscripts at the National Library in Israel, you come up with close to 800 manuscripts of his works.”

Dr. Sasson worked from manuscripts — not in Yefet’s hand, but from as early as the 11th century — to determine the best possible text for the work before she began to translate it.

Her work on Arabic manuscripts reflect a shift in Dr. Sasson’s attitude toward her parents’ native language as she grew older. Before, it had felt like home — something to be outgrown. Later it still felt like home — something comforting to be returned to.

“I felt I missed out on this beautiful language,” she said.

Dr. Sasson moved to America 30 years ago. Her interest in Arabic led her to study at Columbia University, where her husband, Dr. Ron Prywes, is a professor of biology.

Then she discovered that Judeo-Arabic — more about what that exactly is momentarily — was its own discipline, and that a professor at Princeton, Dr. Mark Cohen, specialized in it. She signed up for a course.

“A whole world was open to me,” she said. “He was teaching medieval Judeo-Arabic texts that are amazing.” This led to her earning a Ph.D. from the Jewish Theological Seminary of America.

So what is Judeo-Arabic?

Briefly, it’s the distinctive versions of Arabic used by Jews.

But it’s not so simple.

“There is a big debate now,” Dr. Sasson said. “There’s a scholar at New York University, Dr. Ella Habiba Shohat, who claims that we shouldn’t say Judeo-Arabic, we should just say Arabic.”

That’s because “Arabic has so many dialectics and so many levels. Every ethnic group has its own. Yemenites cannot understand Moroccans, their dialects are so far apart from each other.”

Jews, Dr. Shohat argues, may have spoken a different dialect than their Muslim neighbors. But still, it was closer to their neighbors’ than that of distant Jews.

Yet in the traditional understanding of Judeo-Arabic as a unique thing, there are two possible definitions, Dr. Sasson said. “One says that anything written or said by a Jew in Arabic is by definition Judeo-Arabic. The other says anything in Arabic written in Hebrew characters is Judeo-Arabic.” (As it happened, some of the manuscripts she worked from were written in Arabic characters.)

Yefet’s written Arabic was very different from the language that Dr. Sasson grew up hearing.

“My parents speak a spoken language,” she said. “The topics they discuss are more household stuff. The commentary in a way was academic. Yefet was a sage. It’s a literary language.

“He has his own vocabulary, that repeats itself because he’s talking of certain topics over and over again: wisdom, the wicked, the world to come. The jargon is specific to biblical commentary and the Book of Proverbs, but it is still Arabic,” she said.

Dr. Sasson said that Yefet, not surprisingly, uses his commentary “to promote his own agenda.”

But the bulk of his polemics, at least in his commentary on the Book of Proverbs, are directed not at other Jews but against Muslims and Christians.

“He writes as a representative of the Jewish people,” she said. “He feels connected to all Jews. He is secondarily a Karaite.”

Dr. Sasson likes Yefet’s attitude toward women. He attributes the passage of Proverbs about “The woman of valor” — “Eishet chayil” in Hebrew — to Solomon’s mother, Batsheva.

Dr. Sasson is part of a local group that gathers once a month to practice conversational Judeo-Arabic. But she can’t try it out with her mother.

“Even if I try to initiate a conversation in Arabic, she will go into English,” she said. “The last native speakers of the language, my parents’ generation, are dying. And that’s it.”