She is a Sicilian Saint, who refused to sleep with a powerful Roman in the third Century AD, and was imprisoned, tortured, had her breasts pincered off, still refused to sleep with him and died in prison. She is remembered by cakes shaped as breasts eaten on her feast day of February 5th (I kid you not).
She was martyred in the last year of reign of Emperor Decius (c. 201 AD – June 251 AD) and is thus an early martyr whose cult was established in antiquity, although details of her life and death are, as usual, much later traditions.
It is suggested that illustrations of her severed breasts led the bell founders and bakers to mistakenly adopt her as patron saint as they thought the platter shown in illustrations of the Saint held bells or loaves not breasts! If you seach Google images, you will find most look clearly like breasts, but I guess you could mistake one or two for cakes, but I’ve never seen a bell that shape.