Currently, we cannot use specific keywords as targeting mechanisms in Shopping campaigns (other than those keywords you use in your Titles and Descriptions), but that doesn’t mean you still can’t harness the power of keywords to improve the performance of your Shopping campaigns.
The power of negative keywords, that is.
Use the Search terms report available to you in the Google AdWords interface to run a report which will show you which search terms were actually used by an end user to trigger your Shopping Ads to show in the search results. The Search terms report for Google AdWords is found under Keywords>>Search Terms when you are within a Shopping campaign. Once you pick the desired time-frame you want to view, you can simply put a check-mark into the selection boxes of those keywords you want to add as negative keywords, then add them as either Campaign negatives or Ad Group negatives. By culling through these keywords, you will be able to exclude those keywords that don’t convert , or exclude those keywords that are simply not a good fit for the products your client is trying to sell, and thus avoid wasting your PPC spend on non-productive traffic.
For Bing, you will need to navigate to the Dimensions tab and look under the Search Term column to see the actual search terms being used that trigger for Bing Shopping ads to show in the search results. You can export this data, filter through the data to find the appropriate negative keywords, and then copy and paste the desired negative keywords into the appropriate Bing Shopping campaign.
So don’t forget to use the negative power of keywords in your Google Shopping and Bing Shopping campaigns.