Chrysargyrum

Chrysargyrum (χρυσάργυρον), a tax on trade and commerce under the later Roman emperors, so called because paid in gold and silver; and also tribuium lustrale, because paid once in every five years (lustrum). Even the poorest tradesmen were not exempt from it; and it was called an intolerable tax (φόρος ἀφόρητος, Libanius, Orat. 14, cont. Florent.). Yet Constantius freed the lower clergy, who gained their bread by trade or labor, from this tax; and later emperors confirmed the exemption. — Bingham, Orig. Eccles. bk. 5, ch. 3, § 6.