Trademark law and copyright law are completely different. Stop talking about copyright.
Or do you want to sue everyone that has Andr (Man) in his name?
1) trademark don't cover just exact matches
2) trademarks are in their own classes, you can't litigate across classes
3) common words are perfectly fine as trademarks, as long as commonly associated with a product
Yes exactly and Droid is NOT associated with a Smartphone-OS but Android is.