gridiron

From Middle English gridirne, gredirne, gredyron, gredeyron, grydern, grydyryne, girdirin, girderen, variants of Middle English gredire, gredyre, itself an alteration of Middle English gridel (“griddle”). The ending was assimilated to iron, as if from grid +‎ iron, whence grid was later derived. Doublet of grate, griddle, and grill.

From resembling the shape of a gridiron (a square rectilinear grid).