Significant terms aggregation
One of the aggregations introduced after the release of Elasticsearch 1.0 is the
significant_terms aggregation that we can use starting from release 1.1. It allows us to get the terms that are relevant and probably the most significant for a given query. The good thing is that it doesn't only show the top terms from the results of the given query, but also shows the one that seems to be the most important one.
The use cases for this aggregation type can vary from finding the most troublesome server working in your application environment to suggesting nicknames from the text. Whenever Elasticsearch can see a significant change in the popularity of a term, such a term is a candidate for being significant.