《明史·志·卷六十五》
大将所统率的三个营的士兵，平常称做练勇，有任务时再换名称。
大将所统三营之兵，居常名曰练勇，有事更定职名。
The soldiers of the three camps commanded by the general were usually called lianyong, and the name was changed when there were missions.