Rennie is a Scottish surname of Gaelic origin, derived from the name Rinn, meaning little hill or hilltop. It is believed to have originated in the 14th century, and the name is thought to have been popularized by the Rennies of Scotland, a noble family. Rennie is also associated with the Rennie clan, which was a powerful family in the Scottish Borders. The name has been recorded in various forms throughout history, including Rennie, Rennie, and Rennay. Today, Rennie is a common surname in Scotland and other English-speaking countries.