The term "engineering" is derived from the word "engineer", which itself dates back to the 14th century when an "engine'er" (literally, one who builds or operates a "siege engine") referred to "a constructor of military engines." In this context, now obsolete, an "engine" referred to a military machine, "i.e.", a mechanical contraption used in war (for example, a catapult). Notable examples of the obsolete usage which have survived to the present day are military engineering corps, "e.g.", the U.S. Army Corps of Engineers.