Why are they called scalloped potatoes ?

I thought I might cook scalloped potatoes for a change tonight, but I rarely cook them and wasn't sure of the recipe.  So I grabbed The Joy of Cooking and randomly opened the book in the middle and it opend on the page for scallops.  That's a pretty big book so I figure it's worthy of a Only Coincidence? post.  I ended up abandoning scalloped potaotes and kept it simple with mashed.  Got a little too cocky with the ratios - very creamy.   Well, the kids said very liquidy - but that's not a real word.