X: Beyond the Frontier
Because... an X is a 'cross'... and the adapter crosses over from one connection to the other... and TET is upside down because... reasons?
Wait was 'Beyond the Frontier' a ref to Elite 2: Frontier? I don't think I ever got that before...
*edit* actually Deep Silver picked the X series up and were rumoured to be coming here soon so maybe that WASN'T so random after all...
I was JUST thinking something similar, but more in the X-Com vein.
Cross Communication (the adapter) = Cross-Com = X-Com
As for TET being upside down I'd say it has to do with the angle of the X as opposed to an actual cross; almost as though the X is an upside down cross.