Fade out Effect
noun
The gradual decrease in link value for an external link pointing to a web document from a blog or news source where over time the linking article gradually moves deeper into the linking website’s architecture reducing the value of the links contained within the article and making it more difficult for search engine crawlers and readers to discover.

The fade out effect has impacted the search engine rankings of my friend’s local flower shop website because the article is now 15 years old and no longer linked to from more valuable pages on the local news website.

Explanation
Many news websites and blog websites organize content in chronological order with the most recent content being linked from the home page of a website. Typically, the home page of a website carries the most link value for SEO, in search engines where link values are used to help sort valuable content. When a news article or blog post is fresh and new the link will be one click or tap away from the homepage (one “hop” of a crawler) meaning in most systems it would be closely attached to the highest value page. Over time that article will grow further and further away through the pagination of the website likely (but not always) reducing the value of the article and of the outbound links contained in it. This value loss can often be visualized as a subtle and slow reduction in value over time as the article and website ages and the article becomes increasingly further removed from the most valuable pages on the website. The fade out effect slowly approaches but never reaches zero.

2023 update: Search engines lately have been removing web documents from their respective indices that have dropped significantly in a website’s architecture and have no or little quality internal or external links. Meaning for all useful applications, those documents then have a zero value where as previously the page would simply have an infinitesimally low value. In aggregate these value changes can be quite damaging to overall site rankings and traffic possibly even impacting sales and losing high-value ranking positions. The Fade Out Effect is one major culprit in the de-indexing era of Google specifically and indexing work to improve how many of these documents are added back to and kept in the index may have a significant impact on SEO health.