Biscotto - or
biscuit in French - does in fact mean twice "twice baked". Most biscuits/cookies don't deserve that name as they're baked only once. "Cookie" comes from the Dutch, something like koeken (AnnVan, you can help us there!), which is also the origin of "cake";
pannekoek means pancake.
As for changes in meaning on passing from one country to another, take the Italian word
peperone (note the single
p, by the way), which means a vegetable pepper (e.g. green or red). It's now used, at leaat in GB, to mean a hot spicy sausage (with the
p doubled for some reason).
The Italians play pin-ball. They give it an English name, but not pin-ball. They call it
flipper!
PS Crumpets: I haven't eaten them for years, but I fully share Nona's sentiments! I believe they are what the Americans call English muffins, but not what the English call muffins, which I'm a bit confused about. Sounds rather old-fashioned.