Institutio Oratoria

Augustus again in his letters to Gaius Caesar corrects him for preferring calidus to caldus, not on the ground that the former is not Latin, but because it is unpleasing and as he himself puts it in Greek περίεργον (affected).

Some hold that this is just a question of ὀρθοέπεια or correctness of speech, a subject to which I am far from being indifferent. For what can be more necessary than that we should speak correctly? Nay, I even think that, as far as possible, we should cling to correct forms and resist all tendencies to change. But to attempt to retain forms long obsolete and extinct is sheer impertinence and ostentatious pedantry.