I'm fairly certain that I know the answer to this question, but I want to appeal to the collective wisdom here before I definitively file this in my mind as solved. Is there an earlier source or a similar antecedent to the title Robert Heinlein chose for his novel The Moon Is a Harsh Mistress? The title is so wonderfully evocative and for a long time I thought he must have pulled it from some earlier work, perhaps a poem, in the same way many of Shakespeare's memorable phrases have permeated the works of later writers.
I have searched on and off again for some indication of the source of Heinlein's inspiration without success. Now I think he must have created it from a blank slate.
Interestingly, Jimmy Webb used the title for his song of the same name, with permission from Heinlein's lawyers.
What do you think?