If you are a teetotaler, you stay away from drinking alcoholic beverages.
Some people assume that teetotaler and the related word teetotal were coined to refer to people who totally abstained from drinking anything stronger than tea, but this is incorrect. (Note the spelling difference of the prefix tee.) One theory on the words' origins is that a man called Dicky Turner stuttered in an 1833 speech in Preston, England. He claimed that moderation was not sufficient, instead pledging "t-t-total" abstinence.