Karnatakabhashabhushana 7.16

After adu, idu, and ēn, [the suffix] nitu [occurs] in the sense of measure (pramāṇa).

After these, namely adu, idu, and ēn, the suffix nitu occurs in the sense of measure.

anitu [‘that much’],

initu [‘this much’],

enitu [‘how much?’].

Here, some prefer the doubling of the consonant t—

anittu,

inittu,

enittu.

And likewise is the usage:

“As much as the heavy breasts of the Kirāta maiden with lotus-petal eyes grew, / just so much in the forest did the forester / pare down his bow so as not to bend it too far.”