Macaulay and Targum Onkelos

I have been reading, for months now, T.B. Macaulay's History of England from the Accession of James II. I don't now remember what made me first pick up the little Everyman volumes secondhand; but I quickly realized I was in the hands of a master. Yes, I know about his discredited Whig theory of history and all that. It's true; it's on every page. And yet the book is a forgotten gem of narrative historical writing. His theme really is the Glorious Revolution, what led up to it and what its consequences were; and as Macaulay tells it, it is a gripping story indeed. Say what you want about the Victorians, they wrote incomparable prose.

What leads me to this post, however, is the unexpected mention of an old friend. Macaulay is describing the "nonjuring" clergy -- that is, those who for reasons of conscience refused to swear allegiance to William of Orange. He praises one of them, Charles Leslie, in the following terms:

...he had been studying English history and law, while most of the other chiefs of the schism had been poring over the Acts of Chalcedon, or seeking for wisdom in the Targum of Onkelos.

Now, although I have just been praising him, I am not sure what Macaulay means here. Does he mean that Leslie was studying matters relevant to the issues of the day, while the other nonjurors were wasting their time with recondite books like Onkelos? Or does he mean that Leslie was seeking help from a practical source while the others were trying to find support for their nonjuring stance in books of only remote antiquarian interest? I am inclined to say the former, because I can't imagine what there would be in Targum Onkelos specifically to support the doctrine of hereditary monarchy.

Here's another question: Does Macaulay expect his readers to know what the Targum of Onkelos is? If so, my respect for the Victorian readership would go way up. Or is he just using the vaguely foreign sounding words Targum and Onkelos rhetorically, to denote the esoteric and irrelevant?

I don't know; but it seems to me that it would be interesting to find out if the Targumim were a somewhat known quantity in an earlier stage of English literature.