Donatus, de barbarismo , trans. The Latin text is also available on this server.
Barbarism is a bad part of speech in ordinary speech, in poetic discourse it is called metaplasm.
Tones also are changed in these four types, for they too are added, subtracted, replaced and transformed. Many examples offer themselves, if someone asks. In the same number of ways aspiration also is caught by barbarism, which some ascribe to writing, some to pronunciation, because of h, which, as you know, some consider to be a letter, some the sign of aspiration. Barbarisms also come about through hiatus. Having indicated that one should avoid these errors, we give up the argument about what to call them.