That's a good question. For most of our married life we've owned 2 or 3 dogs at a time, and if we ever mentioned to one dog "where's <other dog name>" they would often go to the other dog so they clearly knew the names we'd given them.
Saying that, though, whenever we'd call one dog's name invariably they all would appear. And they also all answered to 'biscuit' even though that wasn't the name of any of them
Border Terrorist
As for dogs providing their own names... well, we've always named our dogs once we've got them home and thought about it for a while to see what seems to fit. Just over two years ago we brought a new puppy home and took upwards of a week to think of a name for her. It honestly was the most difficult naming process we'd ever had (usually the name had come either on the way home with the puppy, or maybe a day later). We thought we'd finally settled on a name (and actually used it or a day or so) but then discarded it in favour of a different one which suited her better.
Fast forward to late last year when we welcomed another new puppy home. This time it didn't take us long to settle on a name which suited her perfectly. It was a few weeks before we realised that the name we'd settled on, was the name we'd almost used two years ago. And as both names were in a similar vein (both being old-fashioned female names) the two of them 'sounded right' together.
But to make things even more poignant, we sadly lost the first one recently; it seems fate would never allow them to share more than a few weeks together. It broke our hearts and still hurts as I'm sure anyone who's lost a pet will understand. All we can do is treasure the tragically short time we had with her, and we know that she had a hell of a lot of love and a lot of adventure and even if life was too much for her in the end, at least we made it as good as we could for her.
(To make things even worse our elderly dog also passed away just a few weeks after that, so for the first time in a long time, we're down to a one-dog household. We're very protective of our remaining one now and she gets a lot of love and pampering.)