Where did Gibbons get the title "Tanjou" for Attila

One thing that I've never been able to figure out is where did Gibbons, who wrote The Decline and Fall of the Roman Empire, possibly the most famous piece of history on Rome, got the title Tanjou. Of course we're talking about a 200 year old piece of work, but it's something that seems awkward. Could it be a corruption of "Canyu"?

One of the princes of the nation was urged, by fear and ambition, to retire towards the South with eight hords, which composed between forty and fifty thousand families. He obtained, with the title of Tanjou, a convenient territory on the verge of the Chinese provinces; and his constant attachment to the service of the empire was secured by weakness, and the desire of revenge. But the valor of the Huns had extended the narrow limits of their dominions; and their rustic chiefs, who assumed the appellation of Tanjou, gradually became the conquerors, and the sovereigns of a formidable empire. Towards the East, their victorious arms were stopped only by the ocean; and the tribes, which are thinly scattered between the Amoor and the extreme peninsula of Corea, adhered, with reluctance, to the standard of the Huns. On the West, near the head of the Irtish, in the valleys of Imaus, they found a more ample space, and more numerous enemies. One of the lieutenants of the Tanjou subdued, in a single expedition, twenty-six nations... Chapter XXVI: Progress of The Huns.

 

Edited by Imperator Invictus

That would be interesting, but we have very little knowlege of their language.

But as far as we know, it is 100% certain that Attila was Rex Hunnorum. The Romans didn't like to translitterate foreign titles.