Pyeonsu

Pyeonsu is a square-shaped mandu (dumpling) in Korean cuisine. It is a food typically served in summer, served chilled, and dipped in soy sauce and vinegar. The city of Gaeseong in North Hwanghae Province is famous for its pyeonsu. The origin of the word pyeonsu (편수) is obscure. Some claim that it was derived from byeonsi (변시), which appears in the 1527 book Collection of Characters for Training the Unenlightened as a borrowing from the Old Mandarin Chinese biǎnshí (匾食, lit. 'convenient food') that meant "dumplings" at the time. In Korean royal court cuisine during the Joseon era (1392–1897), wheat-skin dumplings boiled in water were called byeongsi (Korean: 병시; Hanja: 餠匙), with the letters byeong (병; 餠; meaning any flour dough food) and si (시; 匙; meaning "spoon") which, combined, could refer to dumplings that are eaten with a spoon. It is also said that the name is Sino-Korean pyeonsu (편수; 片水; lit. 'piece in water'), as the dumplings are served floating on water. Another claim is that the word was derived from Byeon-ssi mandu (변씨만두; 邉氏饅頭), which means "Byeon's dumplings", because it was first made by a person whose family name was Byeon (변; 邉). Although Korean mandu are believed to have first been brought to Korea by Yuan Mongolians in the 14th century during the Goryeo, the variety pyeonsu is thought to be derived from Ming Chinese dumplings brought into the Korean peninsula by the Joseon merchants based in Gaeseong.

Source: Wikipedia