Welcome aBoard, bijoyv--thanks for the good poser!

I think it's an adjectivization (is that a word?)
of come-back. Just a common-sense type deduction. Many
athletes, esp. obstinate ones, make comebacks. At first I didn't think it would fit the material processing example,
but then I thought that perhaps a come-back effect might be a name for something negative--possibly something that causes a setback. Hmm? Lordy, it's good be be back full-time! <grin>