"Kontakion of St Januarius tone 4
The Master has granted thee to Naples, O Saint,/ as a precious treasure and fountain of healings;/ thou art a guardian and protector of the people,/ and dost avert the evils of Vesuvius' fire./ Hence we cry to thee with faith: Rejoice O Januarius, our Father and protector.
Do you know when that Kontakion was written? His greatest intercession concerning Vesuvius didn't take place until 1631. If it was written earlier than that, it would support a history of the Neapolitan people turning to him for centuries.