Why should "we" want to? Or is this an academic query?
If it is, the same question is a good place to start. People need new words, or change the meanings of old ones (both consciously an unthinkingly), because something new is going on - a new country, a new environment, new technology, travel, conquest, discovery, exploration, experiment...
I mean how we can enlarge the word stock of any language without borrowing from other languages. What should be done to protect any language of any nation.. ? Besides acronyms,compounds, back formation etc.,I wonder the other ways.. I expect that there will be some interesting ideas..
I don't believe that this kind of restriction can ever work. It is not natural in any language to have no influences from other languages. Certainly the French - despite their Academie's attempts to prevent "pollution" - use words from other languages freely.