forgotten untranslatable: the poignant sadness you feel for the people your children no longer are.
Once down for her nap, I spent 15 fruitless minutes trying to find it.
Instead I found out that, in other languages, these lists usually include the English word stuff. Which is an excellent word. One that I've noticed non-native speakers often pluralise to stuffs, which is even better.
1: There's probably a word for this.