E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The seven catholic epistles, i.e. one of James, two of Peter, three of John, and one of Jude. The epistles of Paul were addressed to specific churches or to individuals.
The second and third epistles of John are certainly not catholic. One is to a specific lady and her children; and the other is to Gaius. If the word canonical in this phrase means appointed to be read in church, then the epistles of Paul are canonical. In fact there are only five canonical epistles.