I'm with Gunny.... Give it a couple of days - he'll let you know what his name should be.
The big guy in my avatar got named Trooper because the first few days I had him, I had him on long car rides, in strange houses, with other dogs..... etc. He was just a Trooper and didn't let anything bother him.
My other choice was Alfred E. Neuman, but my husband thought I was crazy.