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 earthenware jar, similarly covered with wicker. The capacity of a demijohn varies from two to twelve gallons, but the common size contains five gallons. Ac cording 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.