Kettleby was established no later than 1825, when Jacob Tool of Pennsylvania purchased in a wide ravine, including a stream. He built a sawmill powered by the stream's flow, but little other development occurred in the area. It was the industrious Septimus Tyrwhitt, who purchased of Tool's property in 1842, that spurred development of more mills and the eventual settlement of Kettleby. Early settlers often referred to it as "Tyrwhitt's Mills", in honour of Tyrwhitt. However, he disapproved of the name, and his wife subsequently named the hamlet Kettleby, after the Tyrwhitt family ancestral home in Lincolnshire, England. That the name "Kettle Bee" derived from the construction bee of raising Tyrwhitt's mill, which drew many men from surrounding villages, is a local urban legend. Tyrwhitt was named reeve of King Township in 1852.