Saint Agatha is an important figure from the 3rd century and the artist here styles his subject to appear as her. Some research into the underlayers of the painting has shown that the artist had actually changed his mind midway through developing the artwork and may have had different intentions for the portrait when he first commenced it.
The portrait is dated to around the early 1530s, by which time the artist was fully settled in Rome and his initial Venetian style was starting to fade from his work. Whilst his colours became more sombre there was also a better handling of figurative detail brought about, in part, to the influence of Michelangelo on his skills as a draughtsman.
As with most of this artist's work, it has changed hands on several occasions. The work of the Renaissance masters was in high demand across Europe even from these early days and remains very much as strong in today's global market. Their oeuvre would, as a consequence, be spread right across the continent but many have since been returned to somewhere near their original locations in an attempt to marry artwork with its original communities.
Christianity teaches its followers of the important of sacrifice and also continuing to remember such gestures from others. Saint Agatha is considered a martyr who was tortured for refusing the advances of a high ranking military figure. Such an episode seems highly believable and even in these olden times, such an heroic act would draw favour with people from most backgrounds.