This is probably a Venetian take on the Latin proverb "Omnia Debeo Deo": I Owe Everything to God.
According to Daniel Quinn in his book "Helladian Vistas," a similar inscription dating form 1562 can be found on the ruins of the Byzantine cathedral on the Island of Zantes (Zakynthos), off the west coast of Greece.
The island of Zantes was under Venetian control from 1484 till 1797, so there may be a link between the two inscriptions.
Thanks to Albert from Venice Daily Photo for his important contribution to this post.
Here is a picture of the coastline of Zantes. Stay tuned for the upcoming section: Venice and the Eastern Mediterranean.