The following is what I recall being told by my mother, A”H.
Until the 1940’s, everybody washed their dishes with soap. Jews used “kosher soap,” which I think is still available (in two colors, red and blue) and is made of coconut oil or something like that. Then Tide came out. It was intended for laundry use, but since it wasn’t made of animal fat like regular soaps, Jews used it to wash dishes.