He has been identified by E. Deutsch with the author of the Targum of Onkelos.
"A Biographical Dictionary of Freethinkers of All Ages and Nations"
Joseph Mazzini Wheeler
When Isaac was five years old, his father himself taught him Hebrew, and then sent him to school, where he made rapid progress in learning, so that at the age of eight he could read the Pentateuch with the Targum and Rashi's commentary.
"Some Jewish Witnesses For Christ"
Rev. A. Bernstein, B.D.
The "mosaics" were collected not only from the Bible; the Targum, the Mishna, and the Talmud were rifled of sententious expressions, woven together, and with the license of art placed in unexpected juxtaposition.
"Jewish Literature and Other Essays"
Gustav Karpeles