solidus

ソリドゥス　—　Names of money

The gold coin of later Rome. It held its fineness for a long time.

Solidus of ConstantineAD 310–313 SolidusAD 312– Solidus of Constantine320 AD

⚠ In contrast to silver coins, which were continually debased, this gold coin maintained its intrinsic value. This well-preserved gold coin was trusted even outside the country of issue and continued to be used for international payments over a wide area.

The word meaning "solid" became its name.