The Domestic Sutras of Gobhila

The praise of those who have reached their season original: "rtumatyah" — girls who have attained puberty for the performance of domestic rites. Therefore, even Manu says: "The husband receives the wife given by the gods, not by his own will (9.95)" This implies that marriage is a divinely ordained duty rather than a pursuit of personal lust. Thus, the result is that a girl who has attained her youth should be accepted, and one who has only just approached youth should not yet be married.

Commentary:—A girl who does not feel shame while playing in a naked state is called Nagnika Nagnika: literally 'the naked one,' referring to a prepubescent child. In contrast, a girl whose monthly season has manifested, and has thus attained youth, is called Anagnika. Only the Anagnika girl is considered best for marriage; if such a girl is not available at the proper time, then one whose youth has just begun showing early signs of puberty is also eligible to be wed.

If someone should raise an objection to this based on the following verses:

At eight years old, she is Gauri; at nine years, she is Rohini.
At ten years, she is called a Kanya (maiden), and beyond that, she is Rajasvala original: "menstruating". || 1 ||

The mother, the father, and the eldest brother as well—
These three go to hell upon seeing the maiden menstruating [unmarried]. || 2 ||

That is to say: an eight-year-old is Gauri, a nine-year-old is Rohini, a ten-year-old is called a Kanya, and after that, she becomes Rajasvala. And if they see the maiden menstruating, the mother, father, and elder brother go to hell.

To the contrary, there are more robust and authoritative verses regarding Gauri, Rohini, etc., which provide the etymology of the word Anagnika as follows:

"One should call a maiden Nagnika until she reaches her monthly course.
One who has reached her season is Anagnika; one should give [in marriage] such an Anagnika. || 13 ||

One who has not reached her menses is Gauri; upon reaching menses, she is Rohini.
One without physical signs [of puberty] is a Kanya, and one without breasts is a Nagnika. || 18 ||

When the signs of puberty appear, Soma enjoys the maiden;
When the breasts develop, the Gandharvas; and with the menses, Agni is said to enjoy her. || 19 ||

Therefore, one who lacks the signs of puberty, lacks menses, and lacks breast development—
A maiden not yet 'enjoyed' by Soma and the others is not praised [for marriage]." || 20 ||

That is to say:—As long as a girl does not have her monthly period, she is called Nagnika. Therefore, one should only marry a girl who is Anagnika meaning she has reached physical maturity. || 17 || A girl who has not yet attained her monthly flow is called Gauri, and one in whose body the 'seed' original: "rajas" — menstrual flow has appeared is called Rohini. A girl who shows no signs of youth is called a Kanya, and one who is 'chest-less' (without breasts) is called Nagnika. || 18 ||

Verse 19 refers to the traditional belief that three deities preside over a girl’s development before her human husband: Soma (the Moon) grants her coolness and purity when she matures, the Gandharvas (celestial musicians) grant her beauty and voice when her breasts develop, and Agni (Fire) grants her the power of the womb at menstruation.