Out of curiosity I looked up one of the uses Augustine makes of the linguistic analogy for the Incarnation in De Trinitate; I know there's another one somewhere, but I couldn't find it offhand. I am using Hill's translation:
Thus the word which makes a sound outside is the sign of the word which lights up inside, and it is this latter that primarily deserves the name of 'word.' For the one that is uttered by the mouth of flesh is really the sound of a 'word,' and it is called 'word' too because of the one which assumes it in order to be manifested outwardly. Thus in a certain fashion our word becomes a bodily soudn by assuming that in which it is manifested to the senses of men, just as the Word of God became flesh by assuming that in which it too could be manifested to the senses of men. And just as our word becomes sound without being changed into sound, so the Word of God became flesh, but it is unthinkable that it should have been changed into flesh. It is by assuming it, not by being consumed into it, that both our word becomes sound and that Word became flesh.
Therefore if you wish to arrive at some kind of likeness of the Word of God, however unlike it may be in many ways, do not look at that word of ours which sounds in the ears, neither when it is uttered vocally nor when it is thought of silently. The words of all spoken languages are thought of silently, and people run over songs in their minds while their mouths remail silent; and it is not only the number of syllables either, but the notes of the melodies as well, all of them bodily realities pertaining to the bodily sense called hearing, that the thoughts of those who are thinking them over, and silently pondering them all, find ready to hand in their own kind of non-bodily images. But we must go beyond all these and come to that word of man through whose likeness of a sort the Word of God may somehow or other be seen in an enigma.
(Augustine, The Trinity. Edmund Hill, O.P., tr. New City Press (Hyde Park, NY: 1991) 409-410. The section is XV.20. A different translation can be found online.)
I find this very interesting, since 1) he notes (albeit briefly) that there are disanalogies even in the case of the interior word; 2) his primary interest in the linguistic analogy - here, at least - is to insist that the interior word is a better analogy to the divine Word than the word of speech; 3) the two features he isolates out as analogous to the incarnation are (a) words are signs manifesting the interior word as the incarnate form of the Word is a sign manifesting the divine Word; (b) the interior word is not 'consumed' by being embodied as the divine Word is not 'consumed' by being embodied, i.e., neither are 'changed into' the thing into which they are embodied (in the sense that they simply transmute into them). What is particularly interesting in this bunch of interesting things is the use of the linguistic analogy to the Incarnation to insist that we should do better than the linguistic analogy for the Trinity; it's a surprising twist, although it makes sense - if the word of speech is more analogous to the Incarnation, it's better to use the interior word embodied in the word of speech as an analogy for the divine Word itself.
