I’ve always used the expression “hone in on.” Before I saw this post on World Wide Words, I had no idea that the original is actually “home in on.”
The history is interesting. According to Quinion, early pilots “were said to home on the [radio] beacons.” Then, “after [WWII], people began to use it in the current figurative sense of focusing one’s attention on a single matter.”
Without knowing the original context, though, “home” doesn’t seem to make much sense. So people started changing it:
In this case, it seems to be the figurative sense of the verb to hone, meaning to sharpen a tool, that has led to the change, since it’s widely used to mean making something work better, for example when we say somebody is “honing her skills”. If you are honing in on a topic, you can imagine people thinking, then you’re improving your understanding of it.
This phenomenon is called an eggcorn. Another example is when people mistake “Alzheimer’s disease” for “old-timers’ disease.” It seems plausible enough, right?
With Google Ngram Viewer, we can track the use of both phrases:
Both have generally risen in popularity over time. While “home in on” is still most frequent, the gap has narrowed and “hone in on” may well overtake it in the coming years.