There might be several reasons why you'd want to de-optimize a keyword. You may be facing keyword cannibalization issues where Google is unsure which page to prioritize in rankings. There may have been a shift in your SEO strategy, or your page content has evolved. Regardless of the motive, it's crucial to de-optimize the keyword whenever necessary.

De-optimizing a keyword can be as simple as removing it from the page's metadata and body text. This is particularly useful when the keyword no longer aligns with the page content.

Another strategy is to modify phrases in your content so they no longer contain the exact keyword yet retain their original meaning. This is a subtle and effective approach to keyword de-optimization. It can also allow you to optimize the old keyword on new pages and not have too similar content.

Further, reconsider internal links that feature outdated keywords. It's key to ensure that no internal links utilize the same keyword for different pages, especially if you optimize that keyword for another page.

By following these strategies, you'll effectively de-optimize a keyword, making your content more relevant and better suited to your updated SEO strategy.