Euclidean distance from zero

I am trying to create my own weights for relative work task importance, or weight. For every task, I have a value of importance, frequency, and relevance. I was recommended to use Euclidean distance from zero to create the weight per task. However, I can’t seem to find anything on the internet, why to use such measure at all, and also why it would be better than simply the average of all three.

Is there any specific term for "Euclidean distance from zero" so that I can dig into the pros and cons?