I remember reading an old parable about a woman who always cut off the ends of her meatloaf before serving it. At one point someone asked her why she did that, and she said that her mother had always done it that way. So she went to ask her mother, and got the same answer. The two of them went to the woman’s grandmother who said that the serving plate she cooked the meatloaf was too small, so she cut off the ends to make it fit. I have many doubts that this is true, but also I think it does illustrate a good point about how these things get started.
Most of my family’s “secret” recipes come from a big Soviet cookbook, but adapted for limited availability of products (cooking in Moscow where the book was published was always very different than cooking in Soviet Ukraine).
I actually wonder how many of the Blue Apron/HelloFresh recipes will wind up being “secret family recipes” in a few years.