companheiro de diligência

16:51 May 5, 2020 

This novel is set in ancient Greece, so we're not working within a present-day police system (and I don't think the roles map exactly onto the ones we have today). My concern about "bailiff" is that in the US, we tend to assign that title to the people who provide security within a court.

15:44 May 4, 2020 

But the speaker is a "police magistrate:

"a civil officer charged with the administration of the law. a minor judicial officer, as a justice of the peace or the judge of a police court, having jurisdiction to try minor criminal cases and to conduct preliminary examinations of persons charged with serious crimes."

15:12 May 4, 2020 

It could have something to do with "oficial de diligências", "bailiff", so it could mean "co-bailiff" or "fellow bailiff", in the sense that this "ócio" is something that "keeps him company" at work, when he does not really have any work to do. Could you provide more context?
Some examples:
Forbes insists. “Have you got any better ideas of what it might be if it isn't a UFO then, Craig?” Tyler wonders looking for a plausible solution from his fellow bailiff.
He addresses his supposed fellow bailiff very politely as brother and with the deferential pronoun yow.
Sheriff Paul Bailey, who delivered the tragic news to the public a week ago, said he's still hurting from losing two friends, Kienzle and fellow bailiff Joe Z.