'rube' originates from American English, specifically the given name 'Reuben', where the name was used stereotypically to represent a country person.

'rube' changed from the familiar use of the proper name 'Reuben' in colloquial speech and comic depictions for an unsophisticated rural character and eventually became the modern English slang noun 'rube'.

Initially it referred to the proper name 'Reuben' (or a person called Reuben); over time it evolved into its current meaning of 'an unsophisticated or naive country person' and later broadened to mean any gullible or naive person.