Mantu is a mysterious word found the whole width of Asia, from Japan to the Mediterranean. It can refer to an appetizer, an entree or even a sort of sweet.
In Japan, a manju is a steamed bun made from leavened dough. It always has a filling, usually sweetened bean paste but occasionally pork, making something like jing char siu bau, the steamed pork buns you get at Chinese dim sum restaurants.
But in Korea, mandu are the meat-filled ravioli that show up in Korea's national dish, the soup called mandu kuk. And in China, mantou is a globular steamed bread without a filling. Since mantou is the only unstuffed member of the family, it's assumed that the Chinese used to make it with a filling but at some point stopped (or perhaps just started calling the stuffed version jing char siu bau).
Meanwhile, the nomads of Central Asia make rather large ravioli-like mantu, which they cook by steaming. The filling can be meat or pureed vegetables.
From Central Asia, mantu reached Turkey and Armenia, where it's usually pronounced manti. Here at the western end of the mantu belt, it's a sort of open ravioli, not closed at the top. They're crowded together in a shallow pan like a fleet of tiny meat-filled canoes and poached in stock.
Historians used to assume that mantu was a Chinese invention. But a scholar named Paul Buell has pointed out that when the name mantou first shows up in Chinese writings, it's spelled with a variety of characters, usually a dead giveaway that Chinese writers are trying to represent a foreign word in their non-alphabetic writing system. Eventually they settled on spelling mantou with characters that literally mean "barbarians' heads." Which has rather a derogatory sound, particularly when you remember that the Chinese version is empty.