A fun look at the meaning of "fordern" and "fördern" and what demanding has to do with support, challenges and mining. In short: lots of useful words.
forder, fördern, die Forderung, die Förderung, befördern, erforderm, herausfordern, auffordern, unterfordern
The core idea of this root was:
The root got extended to *dlong- and the d slowly disappeared. The original sense is still very much at the center today, as you can see in offspring like long, length, longitude or elongate.