"of many kinds; numerous in kind or variety; diverse; exhibiting or embracing many points, features, or characteristics," Old English monigfald (Anglian), manigfeald (West Saxon), "various, varied in appearance, complicated; many times magnified; numerous, abundant," from manig (see many) + -feald (see -fold). A Proto-Germanic compound, *managafalþaz (source also of Old Frisian manichfald, Middle Dutch menichvout, German mannigfalt, Swedish mångfalt, Gothic managfalþs), perhaps a loan-translation of Latin multiplex (see multiply).
It retains the original pronunciation of many. Old English also had a verbal form, manigfealdian "to multiply, abound, increase, extend;" in modern times the verb meant "to make multiple copies of by a single operation." Related: Manifoldness.
in mechanical sense, "pipe or chamber, usually of cast metal, with several outlets," by 1855, a shortening of manifold pipe (by 1845), which originally was used with reference to a type of musical instrument mentioned in the Old Testament. See manifold (adj.). As "pipe running from a carburetor to the cylinders in an internal combustion engine of an automobile," by 1904.