Why is the ninth month called September?
"state of having two wives or husbands at the same time," mid-13c., from Old French bigamie (13c.), from Church Latin bigamia, from Late Latin bigamus "twice married," a hybrid from bi- "double" (see bi-) + Greek gamos "marrying" (see gamete). The Greek word was 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.