What is the meaning of the "-osic" suffix on a metal (e.g., cobaltosic oxide)? I just came across the term cobaltosic for the first time in the abstract of Ind Eng Chem Res 52(18): 6076, 2013 (emphasis added):


  A nanocomposite of cobaltosic oxide and nitrogen-doped graphene ($\ce{Co3O4}$/N-G) was prepared by the facile hydrothermal method. 


I assume this is a historical name; Wikipedia's article on the cobalt spinel mentions cobaltosic oxide as an "other name", but provides no other historical information.  Google searches on manganosic oxide and ferrosic oxide turn up the sort of results I would expect, though not all consistent:

Manganese


Analogous to cobalt, manganosic oxide appears to be the $\ce{Mn3O4}$ spinel; e.g., see the abstract here (PDF at link).


Iron


The term ferrosic appears to refer (at least) to a mixed-oxidation state hydroxide, $\ce{Fe3(OH)8}$; e.g., here.
However, it is also used to refer to the iron $\ce{Fe3O4}$ spinel (magnetite); e.g., here.


What is the meaning of this "-osic" suffix?
In the course of searching for examples of usage of the "-osic" suffix, I think I found the answer to my own question.  From the last link in the question, a web store selling pigments (emphasis added):


  The source of natural black oxide usually is from an iron ore called magnetite. Magnetite, also known as lodestone, is a ferrous ferric oxide (ferrosic oxide) that is a heavy, black color and opaque. 


So, it would appear that the suffix indicates a compound of mixed oxidation state: a combination of -ous and -ic forms of the metal.