The word "teetotaler" is supposed to come from the term "total abstainer". At one time, the story goes, it was common in slang to prefix a word with its own first letter to express emphasis or definiteness -- hence, a "T-total abstainer". A similar formation in modern slang might be the use of "period" (or "full stop") at the end of a sentence to indicate definiteness, as in: "He doesn't drink alcohol, period."