Proper noun
Gwatkin
A patronymic Welsh and English surname; derived from Watkin a pet name for the given name Walter. Originally 'ap Gwatkyn' or 'ap Gwatkin', meaning 'son of Watkin'.
The subject of the painting is not known, although conjecture includes Theophila Gwatkin, his great niece, and Lady Anne Spencer, the youngest daughter of the fourth Duke of Marlborough. Source: Internet