Hello Sundari,
I see these quotations from various texts embedded in the commentary Tattvabodhinī on Bhaṭṭoji's Siddhānta-Kaumudī, on rule 3168 of SK [p. 531, edition of SK with Tattvabodhinī, edited by Wasudev Laxman Shastri Panshikar, 7th edition, Nirnaya Sagara press, Mumbai, 1933]: These are comments on the word gaurī:
"गौरी त्वसञ्जातरज:कन्याशङ्करभार्ययो:" ... इति मेदिनी ।..."अष्टवर्षा तु या दत्ता श्रुतशीलसमन्विते । सा गौरी तत्सुतो यस्तु स गौर: परिकीर्तित: ।।" इति ब्रह्माण्डवचनं श्राद्धकाण्डे हेमाद्रिणोद्धृतम् । एतेन "गौर: शुच्याचार:" इत्यादि भाष्यं व्याख्यातम् ।
The end of the above passage uses the quote fromthe Brahmāṇḍa-Purāṇa to argue that the word gauraḥ used by Patañjali in defining a Brāhmaṇa does not refer to the skin color, but it has a Dharmaśāstric significance as "the son of a woman who was given at her age of eight to a learned and righteous Brahmin." The same quote is used by the great Nāgeśabhaṭṭa in one of his commentaries. I have cited that in one of my publications, and I have to hunt down that reference. But it is exactly the same argument.
On a personal level, the history of my own family shows the gradual change from that old standard for the age of marriage. My grandmother was married when she was 9. My two paternal aunts were married at the age of 14 or 15, and since that was considered rather too late, they were married to widowers. My own mother was married at her age of 16. This is an interesting trajectory of history within a single family.
With best wishes,
Madhav M. Deshpande
Professor Emeritus, Sanskrit and Linguistics
University of Michigan, Ann Arbor, Michigan, USA
Senior Fellow, Oxford Center for Hindu Studies
[Residence: Campbell, California, USA]