DOUBLE, twice as much, or large, having two parts, having a part repeated (from the Mid. Eng. duble, through the Old Fr. duble, from Lat. duplus, twice as much). The word appears as a substantive with the special meaning of the appearance to a person of his own apparition, generally regarded as a warning, or of such an apparition of one living person to another, the German Doppelganger (see APPARITIONS). "Double" is also used of a person whose resemblance to another is peculiarly striking or remarkable, so that confusion between them may easily arise.
Double or doubles, in music, is an old and now obsolete term for instrumental variations, derived possibly from the fact that more often than not each succeeding variation "doubled" the notes of the preceding one, two quavers taking the place of one crotchet, and so on. The word "doubles" is also applied in bell ringing terminology to a "change" in which two pairs of bells change places.