Rapscallion, Radical, Reef, Rope's end, Row....

The Pirate Encyclopedia T-shirt is a visual depiction of a letter that people have long know pirates to be fond of.

Actually, I didn't know it. I though it was just a sound they made and in that sounds standard spelling, it begins with a "A." Like, "Arrrr!!" - right? I even checked out multiple online pirate dictionaries (here, here and here) and the like and my findings are in fact yielding the sassy and sophisticated letter "S" as the favorite of pirates, by far.

But, whatever, it's on this shirt so it's obviously factual.