WWE filed for a couple of ECW trademarks, according to WrestlingNews.co. 

WWE filed for Barely Legal and CyberSlam, which were ECW pay-per-view events. Barely Legal was the first ECW PPV that aired in April 1997, while Cyberslam ran from 1996-2000.

The trademarks are for the following:

“G & S: Entertainment services, namely, a show about professional wrestling; entertainment services, namely, the production and exhibition of professional wrestling events rendered live and through broadcast media including television and distributed via various platforms across multiple forms of transmission media; providing wrestling news and information through broadcast media including television and distributed via various platforms across multiple forms of transmission media; providing information in the fields of sports and entertainment through broadcast media including television and distributed via various platforms across multiple forms of transmission media; providing a website in the field of sports entertainment information”

It is unknown exactly why WWE registered but it could be to bring them back as special events on the WWE Network, or merely to retain the rights.