A joke is a display of humour in which words are used within a specific and well-defined narrative structure to make people laugh and is not meant to be taken seriously.
It takes the form of a story, usually with dialogue, and ends in a punch line.
Only one of many broadsides archived in the Harvard library is described as "1706.
As for its being "oral," it is true that jokes may appear printed, but when further transferred, there is no obligation to reproduce the text verbatim, as in the case of poetry.
It is in the punch line that the audience becomes aware that the story contains a second, conflicting meaning.