"one-fourth of a gallon," early 14c., from Old French quarte "a fourth part" (13c.), from Latin quarta (pars), from fem. of quartus "the fourth, fourth part," which is related to quattuor "four," from PIE root *kwetwer- "four." Compare Latin quartarius "fourth part," also the name of a small liquid measure (the fourth part of a sextarius), which was about the same as an English pint.
