The short answer is, Belgian.
The long answer is this: the name Truax comes from du Trieux, and virtually all Truaxs are descended from Philippe du Trieux, who was born in 1588 in Roubaix (currently in France, at the time it was part of the Lower Netherlands). Philippe was a Walloon, which is a group of French-speaking, mostly Protestant people who lived in the area of the Netherlands that is now Belgium and the Artois region of France.
As a Protestant, Philippe fled the Spanish-controlled region in which he was born and moved to Leiden, Holland. In 1624, he emigrated with his family and was among the first settlers of New Amsterdam, now New York. By the time his grandchildren had grown up, they had 'anglicized' the name du Trieux to Truax, Truex, Trueax and other varients.
So there you go! If you want more information on the Truaxs, or would like to query my Truax database, check my website at http://homepages.rootsweb.com/~truax