Merriam-Webster's Collegiate® Dictionary, 11th Edition
GRIT
I. noun
Etymology: Middle English grete, from Old English grēot; akin to Old High German grioz sand Date: before 12th century
1. sand , gravel , a hard sharp granule (as of sand), any of several sandstones,
3. the structure of a stone that adapts it to grinding, the size of abrasive particles usually expressed as their mesh, firmness of mind or spirit ; unyielding courage in the face of hardship or danger, a Liberal in Canadian politics,
II. verb (gritted; gritting)
Date: 1762
intransitive verb to give forth a grating sound, transitive verb to cause (as one's teeth) to grind or grate, to cover or spread with grit