OK, have to approach this from several directions.
1: I had used "XH" as a handle in several places, but I was getting tired of having to add a string of numbers to it.
2: In the Metal Gear series, codenames often take "adjective-animal" form.
3: One day, I was registering on a forum (not this one) and I had just been reading "Last Days of Foxhound" at
www.gigaville.com , which is a Metal Gear parody comic. Hence, I had both Metal Gear and silliness on my mind.
4: Taking that them and mixing it with "XH" resulted in X-ray Hound.
5: In the vein of silliness, I decided I came by this codename by displaying the freakish ability to see through glass.