That’s the term for wedge-shaped slices of shortbread. As to where it comes from there’s only speculation. Some say it’s because the shape resembles actual garments worn by Scottish noblewomen, which strikes me, frankly, as bull. Other say it’s an English corruption of the French words petites gatelles or possibly petits cotés. I’m not qualified to speak on that, but if forced to choose, I’d take the latter explanation. Can I pick ‘none of the above’?
Reader Chana adds:
I never heard the term “petticoat tails” before, but I think it’s cleverly descriptive. It does look sorta like a petticoat tail. Hold up a wedge of that shortbread. Hold it with the sharp angle — the very pointy, acute part — at the top; that is the waist. (That must have been quite a corset!) And the broader part is the bottom of the petticoat. The skirt gets wider as it falls down to the ground. Or think of it as the “train” attachment on a wedding gown. Can you picture it? (If yes, you may eat the shortbread.)