I asked the informant (my mother) to think of any family superstitions other than the most common ones — opening an umbrella indoors, etc. She responded with one I had never encountered before.
Okay, there was a rule: no whistling allowed inside the house. It was bad luck. And that was passed on from Grandpa S—-’s family, so — so no whistling was allowed in my house, because no whistling was allowed in their house, in the G—- house, of Papa U— and Grandma G— and their four kids, because… whistling in the house meant you were gonna have bad luck.
I had absolutely never heard of such a superstition, as my mother did not continue to practice the rule of her parents and grandparents, but a Google search revealed that this superstition is common in Russia. My family did have Russian roots, and given the proximity of Russia and Romania, it is possible that my great-grandparents, referred to here as Papa U—- and Grandma G—-, learned this superstition in their native Romania. More on this superstition can be found here and here. According to these sources, the superstition is linked to money: whistling in the house will supposedly cause financial misfortune. As immigrants in a new country, my great-grandparents clearly did not want to take any chances on losing money, and neither did their son, my maternal grandfather (Grandpa S—-).