rear vassal; daimyo's retainer
Historical term from the Edo period and earlier, referring to a vassal who served a daimyo rather than the shogun directly. In the strict hierarchy, a 陪臣 was a retainer of a retainer.
In the Edo period, rear vassals were considered lower in rank than hatamoto who served the shogun directly.
His ancestor seems to have been a retainer of a certain daimyo.
From Middle Chinese 陪臣 (bwoj dzyin), meaning 'retainer of a retainer'. The kanji 陪 means 'accompany' or 'assist', and 臣 means 'retainer' or 'subject'.