We’ll look at the family of die Not and find lots of necessary words - literally :).
die Not, notwendig, nötig, benötigen, der Notfall
A fun look at the meaning of "wehren" and why a damn evolved into all kinds of words for fighting and defending.
wehren, das Wehr, die Feuerwehr, die Notwehr, die Bundeswehr, abwehren, das Gewehr, verteidigen
The original core of this root was a sense of:
death, exhaustion, collapsing
But this soon shifted toward the idea of “lack of something”.
In English to need , and also in the Slavic branch, the sense shifted further toward the idea of need.
In German, it is also about lack, but it kept more of a sense of emergency.