An old English word for three, derived from the old French treis (now spelled trois). The word survives as the name for a three-spot showing in dice or a three card in card games
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}