Before the county of Corvis, there was the Wizard Corvus. Thirteen hundred years ago, a mad powerful wizard had an estate in the area that became the county of Corvis. Over his 800 year span, he created thousands of magikal items of various types and power level, some of which survive to this day.
Common for sailors to get lashings for punishment. Sailors would then get tattoos of god symbols on thier back so the thrasher was less likely to whip the symbol of the god.
Others say symbols bring bad luck. They draw the attention of the god and it could be wrathful.