How are the ‘categories’ in Google Trends arrived at?

I was researching on health insurance, which, in google trends belongs to two categories viz. Health & Insurance. But, the keyword Health Insurance throws very different results in both the categories.

So, how is it that google is able to categorize Health Insurance in both the categories??? On a macro level, i believe what would answer my dilemma is: What is the methodolgy & logic of these categories on google trends???

Here’s how Google explains, in its own words, how they arrive at trend information:

"Hot Trends takes this list to a new level, providing an up-to-date snapshot of what’s on our collective mind – from current events to daily crossword puzzle clues to the latest celebrity gossip. For each Hot Trends result, the associated Google News, blog searches and Google web search results appear, giving users greater context for each result."

This text is taken directly from Google’s press release on the trends’ results.

I’ve linked the press release below for more insight.

Shirley George Frazier
Author and Small Business Expert