Sometime in the latter 1970s Robin Williams and I co-wrote "Step It Out, Nancy," based on the quasi-traditional Irish "Step It Out, Mary." Our song sort of entered tradition itself, with assorted variants popping up in surprising places since then. I know for certain that we didn't write, and never would have written, "purty darling." When she recorded it, Holly Near appended the frankly cringe-inducing verse that begins "I hope you get my meaning...." You shouldn't have to explain to a listener above the age of five or six that murder is not an acceptable solution except in wildly melodramatic ballads.
The inspiration was the Dayhllls's recording of "Mary." Though I loved the melody and the first part of the narrative, I was repelled by the ending, in which the young lovers (he a sailor boy) resolve the problem of parental disapproval by drowning themselves. We set the narrative in Wyoming's Johnson County Wars of the late 19th Century, when juries composed of friends of cowboys and ranch families who'd run afoul of the big landowners refused to convict them. The story is not, however, based on any specific incident.