Historical term for a close attendant or aide, especially in samurai or noble households. Not used for modern personal assistants.
江戸時代、大名には側役と呼ばれる側近が仕えていた。
In the Edo period, daimyo were served by close aides called sobayaku.
Compound of 側 (そば, 'side, vicinity') and 役 (やく, 'role, duty'). The exact historical derivation is uncertain, but it refers to a person who serves closely beside a lord or master.