Many European cultures spell Christopher with a K and thus the short form Kris. There were about 35 baby boys named Kris, just Kris, in the US last year, and only a handful of baby girls -- this after the name ranking in the Top 1000 for both genders from the late 1940s through the 1970s.
However you spell it, it's an appealing name that's in a slump right now because of overexposure. It's also one of the original gender neutral names, paving the way for a new way of thinking about names and gender.