I particularly like the etymology of κακόν because it has been thematically consistent for so many millennia: as a kid, whether it was friends in the Northeast, or South, or Appalachia, in the city, or the country, from any side of the tracks, everyone told their toddlers that gross things are "kaka".
It's silly, but also, it reinforces that this notion is foundational to how we understand the world. It seems almost like a pure preconception: bad is painful is unhealthy.