Hiroshi Lockheimer of the Google team that build the Nexus 5X and 6P is currently answering questions in a Reddit AMA, and one that came up concerns those mysterious letters at the end of this year's devices. Rather than releasing the Nexus 5 (2015) and Nexus 6 (2015), Google tacked on the letter X to the former and P to the latter.
As it turns out, those characters aren't meaningless—to the Google Nexus team, anyway. They say the X stands for the core of the Nexus brand. Think NeXus. 5X, according to Lockheimer, also sounds cool.
The P in Nexus 6P stands for premium. You know, because you're getting more quality for your buck when you spring extra money for Huawei's larger, aluminum device.
Now that that's out of the way, let's all take a moment to imagine how nice a Nexus 5P could be.