Nipping / Mouthing
When puppies nip, the common explanation is teething. That's wrong. The puppy is learning how hard to bite you before you drop it. This is straight from the ACVB's Decoding Your Dog.
I worked with one family: three boys. The oldest refused to walk past the dog — the dog had claimed his socks and growled when he passed. The youngest simply ripped the sock out. He didn't know the dog could bite. That naive confidence reset the dynamic.
Then there's the Paris Hilton dog — the foo-foo toy breed in mom's arms. You reach in, it nips. "This is my mommy, get away." From the dog's perspective, being held is the jackpot — six inches off the ground, now I'm five-foot-five, taller than the Dobermans. The little dog feels invincible in mom's arms.
The fix: correct the behavior, redirect to something constructive, and consider it from the dog's perspective.