In optics it is the process in optical system manufacturing that gives an element, such as a lens, its required shape.
O.E. grindan, forgrindan "destroy by crushing" (class III strong verb; past tense grand, pp. grunden), from P.Gmc. *grindanan (cf. Du. grenden), related to ground, from PIE *ghrendh-"crushing" (cf. L. frendere "to gnash the teeth," Gk. khondros "corn, grain," Lith. grendu "to scrape, scratch").