bigamist (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.

word-forming element meaning "one who does or makes," also used to indicate adherence to a certain doctrine or custom, from French -iste and directly from Latin -ista (source also of Spanish, Portuguese, Italian -ista), from Greek agent-noun ending -istes, which is from -is-, ending of the stem of verbs in -izein, + agential suffix -tes.

Variant -ister (as in chorister, barrister) is from Old French -istre, on false analogy of ministre. Variant -ista is from Spanish, popularized in American English 1970s by names of Latin-American revolutionary movements.