I'm not sure what you mean by "etched" so here's a couple answers and hopefully one will prove usefull.
1) If the glass simply has an aluminum coloured mark embedded on it, you might successfully hand rub it off using a better quality cut polish (for paint)
2) If by "etched" you mean the glass has a low spot worn or a scratch, then be prepared for some serious polishing!
In the glass business we call it "rule of thumbnail"
...if you can catch a nail on it, It's gonna take significant polishing before the surrounding glass is leveled to the bottom of the scratch and it vanishes.
Your good news is that the resulting lens effect (distortion) might not be an issue for you
...given the low down location.
The basic tools you need are a hard felt pad which chucks in a variable speed drill & about a teaspoon of cerium oxide powder. Add a few drops of water and mix the powder into a slurry in a jar lid,
dampen the felt pad with plain cold water,
dip pad into cerium oxide slurry & polish the scratch with firm even pressure, but at a LOW speed to discourage heat buildup.
You'll learn to keep the slurry going by adding water, never let it dry out, that makes heat, then it dries even faster...vicious circle!
Keep it wet and if she overheats walk away.
3) As an alternative you could bring the window to one of the bigger companies who sell glass. They should have some heavy duty machines which make short work of scratches, utilizing special abrasive wheels.
Good luck.
