The neighborhood we live in is called Arlington Heights, and since I grew up around here I always knew about the area and the name. But the part of the Heights I used to frequent, which is where we live now--the center of the Heights, if you will--is only a little bit higher than the rest of Arlington. The rise as you come up Mass. Ave is noticeable, but nothing you'd call steep. Still, it's there; and I always understood that to be the reason for the name. Now, though, that I've had some opportunity to take walks a little further afield on both sides of Mass Ave, I've discovered the truth: this area is called the heights because most of it is what you could call an absolute mountain.
Now, it's not like the ravines around Santa Monica, where the houses cling to the edges of cliffs and people can drop rolls of their back porch down their neighbor's chimney. That was such an extreme situation that the roads could only be in the valleys or along the tops of the ridges, so the layout of the neighborhoods were entirely dictated by the topography. In Arlington they pretended the hills aren't there, and run roads over just about everything. Some of the roads are consequently rather steep. Also, the hills are alot higher here. In Santa Monica the total change in elevation on any particular 'hill' wasn't more than a 100 feet, I think; in our Arlington heights you feel like you need an oxygen supply at the top of some of the more impressive rises.
And then, it's also the case here that we have the biggest hills for some distance around, at least on the east-west axis. You can see down into Boston in one direction from some of them, and then the other way there isn't much in Lexington that can compete (except for maybe the isolated rise, like Whipple Hill). So I can see why early residents were impressed, and I have a new understanding of the 'Heights' label.