I just check the stat of one of my site. I found that google is ranking a longtail keyword which does not appear in the article. The keyword is related to my site of course Don't want to disclose my niche but I can give an example here Say, if I have a website Japanese Culture The site ranks high for "Asian culture" at the same time. And the word "Asian" does not appear in my site at all.
I've seen keywords that aren't related to my content in my analytics, too. I'm pretty sure that Google's smart enough to know that Japanese, Chinese, Korean, Asian, etc are all related and thus rank you appropriately.
I would agree with freelance as even when you just do a search for something you will see results with words highlight that are not the words you types in but more or less the same thing.