Historical term for a close attendant or aide, especially in samurai or noble households. Not used for modern personal assistants.
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.