What two-word term for a burdensome possession originates from a legend in which an angered Siamese king would give a certain gift to a rival, with the subsequent care of the gift driving the recipient to financial ruin?

Pomerania, a historical region in Europe with a name derived from Slavic meaning “by the sea”, and lends its name to a breed of dog, is split between two modern-day countries. Name one of those two countries.