fellow servant
Refers to a person who serves the same master or works alongside one as a servant. This is a relatively rare and somewhat archaic term; modern Japanese more commonly uses 同僚 or 同輩 for general 'colleague'.
He was a fellow servant working at the same mansion.
Compound of 僕 (servant) and 仲間 (companion, colleague). The exact historical derivation is uncertain, but the word follows a common pattern for forming occupational peer terms.