COACTOR. This name was applied to collectors of various sorts, e.g. to the servants of the publicani, or farmers of the public taxes, who collected the revenues for them (Cic. Pro. Rab. Post. 11); also to those who collected the money from the purchasers of things sold at a public auction. The father of Horace was a collector of the taxes farmed by the publicani (Hor. Sat. i.6.86; Suet. Vit. Hor. init.). Moreover, the servants of the money-changers were so called, from collecting their debts for them (Cic. Pro Cluent. 64).

William Smith, A Dictionary of Greek and Roman Antiquities (London: John Murray, 1875), 300.