While this list in Google Webmaster Tools is interesting, it only tells you what words you use on lots of pages on your site, not for what words you are going to rank. Just because a word is in this list doesn't mean that Google is going to put your site in the SERPs for it. Similarly, using a word on more pages on your site to move it up this list does not appear to improve rankings.
I know because I have experimented with it. For a site that I worked with we noticed that our main keywords were in position 10 on this list. We found ways to use them on more of our pages. That did move them up the list, but it did not improve ranking.
If Google is using the number of pages on your site that use a keyword as a ranking signal, it is a very minor one. Rankings are influenced much more by:
- Use of the keyword in the title tag
- Use of the keyword in external link anchor text
- How users behave when they find your site in the SERPs for that keyword.
In the case of "cookies", you aren't using it prominently on your pages. Other sites are not going to cite you as an authority on cookies. Because of these two factors you are unlikely to ever rank for "cookies".
Even if you do end up ranking for "cookies", you won't rank there for long. Users are unlikely to click on your site from the SERPs when it ranks for cookies because they will see that it is off-topic. This low click through rate (CTR) is a factor that Google will use to de-rank sites that are off-topic for a query. The few users that do click to your site are likely to bounce back to the SERPs and click on something else or refine their query. This bounce back rate (BBR) is another factor that Google uses to determine relevancy of a page for a particular query.