x11-apps is for X.org apps.
commit 6872aa2ef549e70fa6bc56bbb89d37efa47e928e Author: Sergey Popov <pinkbyte@gentoo.org> Date: Thu Jan 14 15:22:05 2016 +0300 Move x11-apps/xtitle to x11-misc/xtitle Gentoo-Bug: 571862