Saddasattha

Dear members,

Does anyone have an idea from which grammar is the following quotation
found in the Vimuttimagga?
"State (dhamma) has the same meaning as that of natural state, which is
taught in the Treatise on Grammar (saddasattha).”
Saddasattha was translated by Ehara et al as “science of sound” but
Lance rightly pointed out that it means grammar. Could “saddasattha”
also refer to a particular work? The Chinese word can be singular as
well as plural. The word saddasattha frequently occurs in commentarial
Pali literature.
The Vimuttimaggga is a text lost in the original language, probably
Pali, but extant in a Chinese translation dating from around the second
century and translated into English by Ehara, Kheminda and Soma as “The
Path of Freedom.”
Similar quotations are found in

Dhs-a 40: Dhamma-saddo sabhaavadhaara.naadiatthajotakattena.
M-.t II 281 (Be): Sabhaavo ti pakati-attho hi aya.m dhammasaddo,
jaatidhammaa jaraadhammaa ti aadiisu viya tasmaa.

I could not find it in a grammatical work, but I did not search very well.

Bhikkhu Nyanatusita