Cold brew is old, but nobody can say exactly how old. You'll often hear that 17th-century Dutch traders made it at sea, or that it began with Kyoto's tall drip towers. These are good stories, but we couldn't verify them, so treat them as legend.
What is documented starts in 1964. Todd Simpson, a young chemical engineer, ordered coffee on a trip to Latin America and was served a small carafe of cold concentrate to mix with hot water. Back home he designed a simple brewer for it, the Toddy: coffee steeps in cold water for hours, then drains through a filter as concentrate. The Toddy, named after him, is among the first cold brew devices sold commercially.
Cold brew spread to big chains much later. Starbucks put it on its menus in 2015. The method hasn't changed: coarse grounds, cold water, time, and a good filter.