DCHP-2

quadruplex < blend of Latin quadri- 'four' and -plex 'adj. suffix' DCHP-2 (October 2016)

• n. & adj. — Housing

  a building separated into four residences; fourplex.

  Type: 5. Frequency — The original meaning of quadruplex was "fourfold". There are numerous other meanings, some of them older, such as Thomas Edison's quadruplex telegraph system, and the modern quadriplex baseball field layout. The meaning referring to houses has a history dating back to around WWI. Other, related forms, such as duplex and triplex, fourplex and fiveplex, are much younger (contrary to the etymology offered in COD-2, which gives duplex as the source for quadriplex). Quadruplex appears to be most frequent in Canada (see Chart 1).
  See also COD-2, s.v. "quadruplex", which is marked "Cdn", and OED-3, s.v. "quadruplex" (2), which is marked "orig. and chiefly N. Amer.".

  See also: duplex (def. 1)  fiveplex  fourplex  triplex