All characters that have been inactive since June 22nd, 2014, will have their names changed to placeholders and the names thrown back in the active pool. If you’ve been taking a break and desperately want to make sure that your old character “Boner-Lord” doesn’t lose her name, take heart; the release is happening on June 25th, 2015. Log in once and your name is secure. Otherwise, you just might lose your name.
Source: Official announcement; thanks to Azzura for the tip!