As a person who has not played The Elder Scrolls V: Skyrim, I only vaguely understand the significance of "Fus Ro Dah." The fact that I'm even familiar with it at all is an indicator of how that expression has permeated the culture, and now ZeniMax wants to make sure that they get to cash in. On April 4, the publisher filed six applications with the United States Patent and Trademark Office for the phrase, with the trademarks covering wide range of potential merchandise.
The typical videogame stuff is there, referencing strategy guides, manuals and software, as well as clothing products, bags and art prints. On the whole, rather normal merchandising stuff. This might mean that we're going to see a blitz of licensed products with the expression on it, but I suspect this is more of a move by ZeniMax to protect their intellectual property. Broad merchandising trademark applications like this are fairly common, so we'll have to see how ZeniMax chooses to use it.