Dude" is an informal term used to address or refer to someone, especially in American and Canadian English. Originating from Southern California surf culture in the early 20th century, it was popularized as a greeting and general form of address by movies like "Rebel Without a Cause" (1955) and television shows like "Gidget" (1965-1966). The term is often associated with laid-back, casual attitudes, reflecting its roots in the youth culture of the 1960s. It has since become a ubiquitous part of American slang, transcending age and social boundaries.
"Interesting name trend with Dude! Steady at five births a year from 1912 to 1914 and again in 1929 and 1970. Spikes in 1918 and 1921, then a long gap before resurfacing in the late 60s."