In tenth grade, I was assigned a rather interesting project to do for my Jewish history class. We were to interview a grandparent, have her tell her life story, in so many words, and then research the Jewish history of the country she came from. In my case, I chose to interview my grandmother, whose family hailed from Warsaw, Poland.

Among many of the fascinating things she told me, there was one story that I always go back to whenever I think of that interview. On Thursdays, said my grandmother, nobody in the family was allowed to take a bath. “Why?” I asked her. “Because there was always a fish in there on Thursdays,” she told me.

Her mother, my great grandmother of course, would buy a live fish, put it in a bag of water, and flip it into the bathtub. On Friday morning, she’d beat it over the head with a hammer, open it, clean it, skin it and grind it to bits, bones and all. Then she’d put the ground fish stuff back in the skin, add some spices, and cook it. This is, when it all is said and done, gefilte fish, meaning “filled fish.” Filled with itself in its own skin.

How did this come to be a Jewish fish? Well, barring any serious research, I can take a pretty good guess from a recent carp experience that I had at the Jerusalem market. I didn’t have much cash on me, so I bought a cheap fish, about $2.50 a pound. It was a carp, which is what they make gefilte fish out of. My wife made it, and I realized that it had way too many bones in it to eat it as is. That must have been why it was cheap.

“Is this a carp?” she asked me. I said yes. She told me that you’re not supposed to eat carp whole. You’re supposed to make gefilte fish out of it. That way all the bones are ground up and you can eat it without choking.So then it clicked. If you have a fish that’s $2.50 a pound and you’re a poor Eastern European Jew living in the Pale pre Emancipation, you’re going to buy a really cheap fish and figure out the best way to eat it. In the case of a carp, the only way is to grind the thing up, or spend 6 hours filleting it. Then you bring the custom to America out of habit and put it in your bathtub on Thursdays. Then it becomes a cultural phenomenon.

Now, of course, it’s turned into a “thing” and is way more expensive because it’s a novelty item. But buy a carp whole and you can do it yourself the cheap way. Probably tastier, too. Here’s a good gefilte fish recipe to start.