And - Edit 1
Before modification by Camilla at 02/11/2011 06:39:33 AM
"Mutual" means reciprocal. If Mr. Dickens had even the faintest notion as to how to properly use the English language, he would have named the book Our Common Friend or, if that made the friend sound too plebeian, he could have called it simply Our Friend. After all, the use of the possessive "our" already implies commonality of relationship.
Both of those would have missed out on the cruicial point.
*sniffs indignantly*
I am sure you are exaggerating your seriousness for comic effect, but allow me to observe (for the record -- because this is the internet and someone might pick up your objection as fact) that a)languages change, and this expression has been around since... at least the 1600s, b)Dickens did (demonstrably) know how to use the English language, and.