In reading the Dispeller of Delusion today I came across a rather peculiar passage regarding the "knowledge of dhamma language" also translated as "knowledge of philology":
The passage is commentating on the chapter 15 of the Vibhaṅga:1949. But here, as to saying that beings learn a tongue, this is only when it is told them; for a mother and father, when their children are small, lay them on a bed or on a chair and, speaking such and such words, do such and such work. The children define such and such speech of theirs thus: 'By this that is mentioned, by this that is mentioned.' As time goes on, they get to know the whole tongue. The mother is Tamil, the father is Andhaka. The child born of them, if he hears the mother's speech first, will speak the Tamil tongue; if he hears the father's speech first, he will speak the Andhaka tongue. But not hearing either speech, he will speak the Mägadha tongue. And he who is reborn in a great forest without a village and where there is no-one else who speaks, he too, when he creates speech of his own accord,  will speak only the Mägadha tongue. And in hell, in the animal kind of generation, in the realm of ghosts, in the human world and in the world of deities, everywhere the Mägadha tongue is foremost. 1950. Herein, the rest of the eighteen tongues beginning with the Otta, the Kiräta, the Andhaka, the Greek and the Tamil, change; only this Mägadha tongue correctly called the perfect (brahma) usage, the noble usage, does not change. Also the Fully Enlightened One, in announcing the Buddha word of the Tipitaka, did so only in the Mägadha tongue. Why ? Because in this way it is easy to deduce the meaning; since the only delay for the Buddha word announced in the text in the Mägadha tongue is that occurring when coming to the ears of those who have attained the Discriminations; but when the ear is merely impinged upon, the meaning appears in a hundred ways, in a thousand ways. But a text announced in another tongue has to be learnt by repeated application. But there is no reaching the discrimination for an ordinary man, even if he has learnt much; and there is no noble disciple who has not reached the Discriminations.
https://suttacentral.net/vb15/en/thittilaThe four analytic insights are; The analytic insight of consequence, analytic insight of origin, analytic insight of philology, analytic insight of knowledge. Knowledge of consequence is analytic insight of consequence; knowledge of origin is analytic insight of origin; knowledge of the actual philological definition of these (i.e. 1 & 2) is analytic insight of philology; knowledge of (these) knowledges is analytic insight of knowledge. This is summary section.
I find it peculiar because it seems to be quite a Brahmin view. By that I mean the Brahmins thought of sanskrit as being the "original language", with all other languages being degenerate forms of it. Also, due to their metaphysics, they held that the sanskrit words of their texts directly related to the realities underlying them, and so any change in the word or definition would lead to a loss in understanding that reality. This is obviously a different understanding to the nominalism of the Dhamma. Apart from this, the Buddha in MN 139 rejected such ideas regarding any language being sacrosanct:
I'm therefore interested to know what the commentary is to MN 139 and how the sutta can be reconciled with what currently looks like a rather Vedic misunderstanding in the commentary?Here, bhikkhus, in different localities they call the same thing a “dish” (pāti) or they call it a “bowl” (patta) or they call it a “vessel” (vittha) or they call it a “saucer (sarava) or they call it a “pan” (dhāropa) or they call it a “pot” (poṇa) or they call it a “mug” (hana) or they call it a “basin” (pisīla). So whatever they call it in such and such a locality, he speaks accordingly, firmly adhering to and insisting on that, “Only this is true, anything else is wrong.” This is how there comes to be insistence on local language and overriding of normal usage.”