Most of the Chinese loans entered Oroqen during the 20th century. Before the 1950s, hardly any Chinese resided in the regions where the Oroqen lived and hunted in the Greater and Lesser Mountain ranges. Therefore, the Chinese loans are assigned the age of 20th century. In fact, a handful of the borrowings are clearly very recent because they are terms used in Chinese only after 1949 when the Communists took over the government from the Nationalists.
The Dagur loans were assigned the age of 20th century or earlier due to the fact that some of the borrowings may have entered Oroqen well before the 20th century since the two ethnic groups have coexisted in a mutually dependent relationship for centuries.
Mongolic borrowings are also assigned the age of 20th century or earlier for a similar reason as that of the Dagur. The main difference is that the contact between the two groups was not as intense and persistent as the contact between the Oroqen and the Dagur.
The loans from Russian are mostly given the age of 20th century or earlier because their contact goes far into their history from before their migration into China. Some of the Russian loans are clearly 20th century since they encode 20th century phenomena.
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