I heard the phrase crooked rib when reading Jenny Wormald's "Mary Queen of Scots: A Study in Failure". 
The idea of the crooked rib of course alludes to the story of Eve in Genesis having been born of Adam's spare rib.  Crooked rib suggests corruption.  It's the old idea categorising woman as being either virgin or whore.  The figs being redolent of the forbidden fruit on the tree of knowledge. Figs are such a sexual fruit, the image is of lust and wantonness .  
Wormald was not a fan of Mary.  When she came to discuss the casket letters and the likelihood or not of Mary being the author she examined, in her view, the evidence for whether Mary's pre-marital sexual encounter with Bothwell was consensual or rape. Wormald argued that while in contemporary (trashy) fiction the trope of the woman who falls for a scoundrel  who treats her badly as in many a Barbara Cartland/ Mills and Boon, there were no such examples of such a stereotype in 16th Century writing.  She referred to a study of Medieval women titled "Crooked Rib" in which the author describes women falling into two categories:  the virgin - meek and good and not responsive to rape, and Eve - taunter and instrument of man's destruction and not a candidate for rape (presumably because she would be so up for it !). Wormald argues, spuriously I think, that for the casket letters to have been invention, it would require the author to have been familiar with the stereotype of a woman who's love for a man is awakened by rape (!?!) and that as there was no 16th century contemporary precedent for this, Mary must, in fact have written them herself.  More "evidence" from Wormald is that Mary allegedly (but debatably) said that she would follow Bothwell to the end of the earth in her petticoat.  The consequences of the casket letters amounted to more than just tittle tattle, they were in fact used in her trial which led to her execution.  Lesley Smith, another contemporary historian, is also at pains to prove Mary's guilt by studying "evidence" of Mary's bad morals and therefore her guilt by concentrating on whether her coupling with Bothwell was rape or consensual .  I suspect not but I would wish she had had a lust filled consensual time with him.  It would be a shame if she had no such experience at least at some time in her short youth at liberty.  Darnley, her relationship with whom had already turned sour before they even wed, was certainly putting it about all over the place with men and women and was riddled with syphilis and Francois was sickly and immature.  James V had several mistresses and several illegitimate children. The double standard seems stark now but it seems that people are still prepared to make judgements through the prism of medieval morality to back up their own prejudices.