The name for this, is a completely made up Japanese word. It's no secret that the Japanese have always been, and will continue to be, fascinated by Western culture. As a kid growing up, I spent a lot of time in Japan. I remember my younger self was so confused by all of the graphic tees that would have random English words plastered all over them. An attempt I think, to give Japanese brands a Western edge. I think now, it's cool to see a flip where Westerners are fascinated by Japanese culture.
The word "kame(h)" in Japanese means turtle and "kubi" means neck. It's not a turtleneck though. I got the fabric and the first thing I thought when I saw the roll was, "This is a nice turtleneck fabric." As the shirt started to come to life, the more I thought about it, the more I didn't want to make a turtleneck.
The idea changed, but the name remained...