bigamy (n.)

"state of having two wives or husbands at the same time," mid-13c., from Old French bigamie (13c.), from Medieval Latin bigamia "bigamy," from Late Latin bigamus "twice married," a hybrid from bi- "double" (see bi-) + Greek gamos "marrying" (see gamete). The Greek word was digamia, from digamos "twice married."

Bigamie is unkinde ðing, On engleis tale, twie-wifing. [c. 1250]

In Middle English, also of two successive marriages or marrying a widow.