Sutra:
78. namaSSu na enRum, ma: enRum iraNdu patham.

Meaning:
The nama: is made up of two parts - na and ma:.

Sri PBA Swami's Sarartha Deepikai:
In order to show the meaning of the nama: part, it is broken up further into two parts (avAntara vibhAgam). That is, na and ma:.