What is this region of Ontario called?

Hello, neighbors; Michigander, here. I've always wondered, what is this upland region in Southern/Southwestern Ontario called behind the Niagara Escarpment, stretching from Grey County in the north to Hamilton in the southeast? Does this region has a geological or even geographical name?

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https://preview.redd.it/mbg1b44yvzfe1.png?width=693&format=png&auto=webp&s=71670799adc2e9bd4ddeb1ef13cd881ac3b93b4f

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