DEMIJOHN, a glass bottle or jar with a large round body and narrow neck, encased in wicker-work and provided with handles. The word is also used of an erthenware jar, similarly covered with wicker. The capacity of a demijohn varies from two to twelve gallons, but the common size contains five gallons. According to the New English Dictionary the word is an adaptation of a French Dame Jeanne, or Dame Jane, an application of a personal name to an object which is not uncommon; cf. the use of "Toby" for a particular form of jug and the many uses of the name "Jack."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)