I near lost my scores in Adwords

I nearly lose my score in Adwords just because of 1 keyword. I purchase a keyword called impromptu which is known to me as a report writer. There were a lot of impressions for the keyword but nobody clicked on my ad. I was very puzzled why nobody is interested in my ad. I have an above average click through for other words using the same ad. So I went to search the web using the keyword and was surprised to discovere that the keyword also have other meaning to other users. I immediately stopped advertising using the keyword. Why did I say losing my score in Adwords. If I don't get a good click through, Google will penalise me and that means the next time I set up another campaign, I would have to have to pay more per click because of my histroy here.