Germany is even odder in that way, because we have two words for biscuits and I don't think there is an actual rule which word you use, it's pretty much intuition.
Generally speaking, every Christmas biscuit and everything that sort of comes from a fancy tin or bakery and that you would serve to guests on a plate is a 'Plätzchen'. It's sounds slightly more posh. Everything that you either eat straight from the package or would feed to a small child is probably a 'Keks'. Something you bake yourself could be either, really. And cookies are cookies, because that's the name they are sold under at Subway and in the super markets. Otherwise, a cookie would fall into the 'Keks' category, probably.
Oh, and dog biscuits are 'Hundekuchen' (dog cakes) and Cookie Monster is called 'Krümelmonster' (Crumb Monster), but when he demands COOKIES!!!, it's translated as 'KEKSE!!!'.
("This has been the German Education channel. Have a pleasant day!")
But Sentinels knowledge is useful - how else are you supposed to save the Multiverse?
Regarding biscuits, I'd not heard of Tuille or Sable either. Well, I've heard of sable but to me it's (as well as the antelope) another word for black, taken from the small furry mink-like creature whose fur used to be used for posh clothes or whatever.
I like Bourbons and (Dark) Chocolate Digestives :D. Oh yeah, and Choccy Dodgers (choccy equivalent Jammy Dodgers) are nice too :D. And Toffeepops (actually I think it's spelt Toffypops), they look a bit like small, milke chocolate digestives but they have a layer of toffee beneath the chocolate :D. And I like Jaffa Cakes but I agree that they're cakes, not biscuits, for the already-given reason that biscuits go soft when stale and cakes go hard (which is what Jaffas do). That said, I like Jaffa Cake bars even more than normal Jaffas. Om nom nom!
