What is "thrymsa"

n. An ancient coin, one of the earliest Anglo-Saxon gold tremissis.

The thrymsa was a gold coin minted in seventh-century Anglo-Saxon England. It originated as a copy of Merovingian tremisses and earlier Roman coins with a high gold content. Continued debasement between the 630s and the 650s reduced the gold content in newly minted coins such that after c. 655 the percentage of gold in a new coin was less than 35%. The thrymsa ceased to be minted after about 675 and was superseded by the silver sceat.