Ship, shipper, and the common carrier

In Chapter 1 of  Essentials of Transportation and Public Utilities Law, 2011 Edition by Timoteo B. Aquino and Ramon Paul L. Hernando we learn of parties involved and the two kinds of contract of transportation. 

If it is a carriage of passengers, the two parties are the passenger and the common carrier. In a carriage of goods, the parties are the shipper and again the common carrier. 

Is this perhaps the reason for the term "common carrier", the party common to each kind of contract?

But on page 199 of the book we find a confusion of identity between a shipper and a common carrier:

Checking up on the case law quoted we find that it is the decision that seems to be confused.