[1675–85; tri- + valve]This word is first recorded in the period 1675–85. Other words that entered Englishat around the same time include: constitutional, hustle, muscular, prairie, upstreamtri- is a combining form meaning “three,” used in the formation of compound words. Otherwords that use the affix tri- include: triglyceride, triglyph, trilemma, triple, trivial