Just a brief comment to add to the others.  In the 1880s in America, political economy was a term that had a great deal of current usage.  But economics was beginning to be used as well.  In the historical trends eventually that led to the creation of professional associations in the U. S., a Political Economy Club was organized in America in the early 1880s.  This group tended to espouse the views of Smith, Ricardo, and Mill and were mostly quite conservative.  A "new school" of economists chose to start another group, the American Economic Association."  Note the change in name from political economy to economic. 

One of the members of the "old school" and President of the Political Economy Club, Simon Newcomb wrote:  "'Economics' is a term introduced by recent English writers which has the double advantage of brevity and avoiding the serious objections brought against the current term Political Economy" from his Principles of Political Economy, p. 13, 1886.  Newcomb goes on to use the term "economics" especially in part II of that book.

There is an article about the Political Economy Club by A. W. Coats in the American Economic Review in 1961 and another by Wm. Barber in the Journal of Economic Perspectives in 1987.

Jim  Wible