From Varro, 7.52
“A man speaks [fatur] who first releases from his mouth a sound that has a meaning. From this, children are called infants [lit. the ‘unspeaking’] before they can do this; when they can do this, they are said “to speak”.
Fatur is qui primum homo significabilem ore mittit vocem. Ab eo, ante quam ita faciant, pueri dicuntur infantes; cum id faciunt, iam fari;
Augustine, Confessions 1.8
“Was it really this man—me—who jumped from infancy and moved to childhood? Or was it more that childhood entered me and replaced infancy? Infancy didn’t depart—where would it go? But still, it was not there anymore. For I was no longer an infant who could not speak but I was a boy who spoke. I remember this and sometime later I understood where I learned to speak. My elders were not teaching me, offering me words in some established curriculum as they would later with reading, but I, with the mind you gave me, my God, I wanted to make clear the feelings of my heart with all types of groaning and sounds and mad moving of the limbs, so that my will would be obeyed; when I did not prevail over all the things which I wanted from everyone, I picked at it with my memory. Whenever anyone called something something and when they moved toward a thing in response to that word a second time, I observed it and I understood that the thing was named by them—when they made that sound they meant to indicate it.”
nonne ab infantia huc pergens veni in pueritiam? vel potius ipsa in me venit et successit infantiae? nec discessit illa: quo enim abiit? et tamen iam non erat. non enim eram infans qui non farer, sed iam puer loquens eram. et memini hoc, et unde loqui didiceram post adverti. non enim docebant me maiores homines, praebentes mihi verba certo aliquo ordine doctrinae sicut paulo post litteras, sed ego ipse mente quam dedisti mihi, deus meus, cum gemitibus et vocibus variis et variis membrorum motibus edere vellem sensa cordis mei, ut voluntati pareretur, nec valerem quae volebam omnia nec quibus volebam omnibus, prensabam memoria. cum ipsi appellabant rem aliquam et cum secundum eam vocem corpus ad aliquid movebant, videbam et tenebam hoc ab eis vocari rem illam quod sonabant cum eam vellent ostendere.