Tra từ serf - Từ điển Oxford Advanced Learner 8th

serf [serf serfs] BrE [sɜːf] NAmE [sɜːrf] noun
(in the past) a person who was forced to live and work on land that belonged to a ↑landowner whom they had to obey

Word Origin:
late 15th cent. (in the sense ‘slave’): from Old French, from Latin servus ‘slave’.

Culture:
feudalism
Feudalism is a social system that was introduced to England by the ↑Normans in the 11th century and lasted throughout much of the ↑medieval period (1066–1485).
Under the Normans, English society was divided into a pyramid-like structure with the king at the top, below him the barons, then less powerful local lords, and finally the peasants. An area of land owned by a lord was called a manor and this was the basic farm unit. Lords gave peasants several long strips of their land to grow crops in a system known as ↑strip-farming. In exchange, peasants had to promise loyalty to the lord and do military service when required. Villeins or serfs had a lower status than peasants and had to work a specified number of days on the lord’s land. In 1086 a detailed survey of land was carried out in every village in order to decide its ownership and value, and the information was recorded in the ↑Domesday Book.
The feudal system started to break down in the 12th century, when the king and the barons began to rely on professional soldiers instead of peasant armies. Instead of doing military service peasants paid dues (= money) for working their land. By the end of the 14th century many peasants had bought their land and become the yeomen (= small farmers). The system of holding land with permission from the local lord finally ended in England in 1661, though not until 1914 in Scotland.
The influence of feudalism can still be seen in modern British land law and in the British class system.