Meaning

noun Roman statesman and philosopher who was an advisor to Nero; his nine extant tragedies are modeled on Greek tragedies (circa 4 BC - 65 AD)

noun a member of the Iroquoian people formerly living in New York State south of Lake Ontario

noun the Iroquoian language spoken by the Seneca

originFrom Dutch Sennecaas, from Algonquian (probably Mahican [Term?]).

Etymology from Wiktionary, CC BY-SA 3.0