This pattern is based on an illustration from a 1674 poem, The Devil of Pope-Fig Island. 
Perretta, the hero, tricks the devil into thinking her vulva is actually a wound and gives him a scare...
    Said she, the wretch has used me very ill;
    Of cruelty he has obtained his fill;
    For God's sake try, my lord, to get away:
    Just now I heard the savage fellow say,
    He'd with his claws your lordship tear and slash:
    See, only see, my lord, he made this gash;
 
Magdalena Łanuszka summed it up nicely:
"... a reckless bet between a farmer and the devil: the challenge was to prove which of them could better dig furrows in the ground. The unfortunate farmer’s wife decided to help her husband and showed her body parts to the devil, complaining that her husband had tried out his claws on her body and had scratched her between the legs. The devil, apparently not familiar with female anatomy, believes it to be a terrible wound; scared that his opponent is so mighty, he gives up the challenge and runs away."