“If you shake your leg, your luck will fall away”
My informant shared this superstition as one that her mother’s friends would say to her. She had a habit of shaking her leg whenever she would be sitting, and the ladies of her church always reprimanded her on this habit, stating this superstition. For her personally, she dislikes this saying because it annoyed her when people quoted it to her to scold her for jiggling her leg. She speculated that it probably comes from the idea that ladies should sit still, and such leg jiggling could look unstable. Also, the actual motion of shaking could cause “luck to fall off.”
I have also heard this superstition before. I don’t particularly believe that is has much truth behind it, although I did hear from somewhere that there is a variation of it in which shaking your leg can cause your money to fall away, possibly because shaking your leg could cause your wallet to fall out of your pants. This makes more logical sense, and luck and money can be related concepts. The explanation of the action of shaking being unpleasant to look at also makes sense to me, as it can seem disrespectful, especially at a church in the presence of elders.