Plural of 'grate'; iron bars or grids used to hold burning fuel in a fireplace or furnace, or verb meaning to scrape harshly.
From Old English 'grate,' derived from Latin 'cratis' (wicker work). The word transferred from woven structures to metal grids, and the verb meaning 'to scrape' developed from the harshness of grating action.
It's surprising that 'grate' traces back to Latin 'cratis' meaning wicker—the Romans used woven grates for their fires, and that ancient design principle is basically unchanged in modern furnaces, making it one of history's most durable inventions.
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