On-site SEO aims to establish a collection of keywords that a given website will use to define its identity for search engines so that the site would hopefully appear early in SERPs when users enter these keywords as search queries. In order for the website to rank highly in each of its intended keywords, those keywords would have to be carefully incorporated into the content of the site's pages. Every so often, however, the website's owner may find while using analytics software that the site is receiving a lot of visitors on account of a particular keyword that is arguably not the primary one being focused on. For example, a web page about a legal service relating to a type of product might inadvertently be getting a lot of impressions from users who were searching for a storefront that sells that product. In another example, the website might be receiving impressions for a keyword that is a synonym for another keyword but is much less technical. It does not help the website in the long term if it goes about optimizing its content for every keyword that happens to garner a high amount of traffic for whatever reason. Drawing traffic to the site is only half of what any website trying to maintain a financially stable business needs to be concerned with; it should also be minimizing the rate at which visitors instantly leave the site. These are commonly called "bounces" and usually represent people who did not consider the site to be what they were looking for. When faced with keywords that incidentally bring traffic, the web owner must selectively optimize the ones that would logically be what the intended audience would be searching for. Popular keywords that happen to be non-technical versions of other core keywords are good to optimize because they would usually be searched for by people who are not knowledgeable about the website's industry but are willing to learn about it. Keywords that are irrelevant to the site's purpose should be kept defunct so that the site does not receive potentially misled visitors. For more information click here https://www.reddit.com/r/SEO/comments/9jvu3e/gettingimpressionsforanunexpected_keyword/.