Why is Fido such a common name for a dog when in reality no one really names their dog Fido?
Fido was the name of Abraham Lincoln's dog. He left Fido behind in Springfield (Illinois) in the care of another family when he went to Washington D.C. to take the Presidency. Fido died shortly after Lincoln was assassinated.
Fido is a latin word meaning "I trust"
I'm not so sure that it is, at least in the US.
Everyone in our family has always had dogs, as have all of my friends and not one dog was ever named Fido or even something similar.
My grandfather who was an Iowa farmer had a series of dogs named Fido as did our neighbors to the east. Perhaps it's an Iowa farm name.
Since the origin of firehouses, dogs were mascots. All firehouses named their resident dog, "firehouse dog". Where's the "firehouse dog"? was truncated to "where's Fido"?
The truncation quickly spread to the general population and was widely used. I haven't heard it used for the last 60 years.
Fido in latin can be translated as faithful, as dogs are considered to be. For cats Felix can be translated as happy or independent.