A cooking utensil with parallel bars for grilling food; also, the field where American football is played.
From Middle English 'gridire,' from Old French 'gredil.' The word combines 'grid' (a cooking surface with bars) and 'iron' (the metal). It originally referred to a grill, then became slang for a football field.
It's wild that 'gridiron' started as kitchen equipment—American football fields got this name because their yard-line markings look like the parallel bars of a cooking grill, making it a perfect example of how specific objects become slang for completely different things.
Complete word intelligence in one call. Free tier — 50 lookups/day.