"pledged to total abstinence from intoxicating drink," 1834, a word possibly formed from total (adj.) with a reduplication of the initial T- for emphasis (T-totally "totally," though not in an abstinence sense, is recorded in Kentucky dialect from 1832 and is possibly older in Irish-English).
The use in temperance jargon was first noted September 1833 in a speech advocating total abstinence (from beer as well as wine and liquor) by Richard "Dicky" Turner, a working-man from Preston, England. Also said to have been introduced in 1827 in a New York temperance society which recorded a T after the signature of those who had pledged total abstinence, but contemporary evidence for this is wanting, and while Century Dictionary allows that "the word may have originated independently in the two countries," OED favors the British origin and notes that Webster (1847) calls teetotaler "a cant word formed in England."