My informant is the daughter of Romanian immigrants. She shared with me a superstition that he heard from her mother.
According to my informant’s mother, if you’re sewing something, you need to keep a string in your mouth. Otherwise, evil spirits will sew your mouth shut, Alternatively, you could lose your wits and become stupid.
I can relate to the entirely unfounded feeling of security found in these practices while performing tasks like sewing. It reminds me of the discomfort I feel when I am performing a task that could go badly, and I do some strange unrelated gesture that convinces me that I am protected from this bad outcome.