"three-part altar-piece carvings or pictures hinged together," 1849, based on Italian triptica, from tri- "three" on model of diptych.
Entries linking to triptych
tri-
word-forming element meaning "three, having three, once every three," from Latin tres (neuter tria) or Greek treis, trias "three" (see three).
diptych n.
1620s, "hinged, two-leaved tablet of wood, ivory, etc., with waxed inner surfaces, used by the Greeks and Romans for writing with the style," from Latin diptycha (plural), from late Greek diptykha, neuter plural of diptykhos "double-folded, doubled," from di- "two" (see di- (1)) + ptykhe "fold," which is of uncertain etymology. In art, "a pair of pictures or carvings on two panels hinged together," by 1852.