I was thinking a portmanteau of “strength” and “stealth”. Which appears to be what hajario was thinking, too, but I took it in a different direction: Strength by virtue of stealth. It’s no secret that a B-2 or F-117 is a powerful airplane, but it’s powerful because it’s stealthy.
Stealthily stretchy - you know how when you stretch spandex, it makes the faintest if sounds? Well, with strelth fabric, ninjas, Navy Seals and Army Rangers can get their yoga on and kill you before you ever hear them.