late 14c., incorporacioun, "act or process of combining substances; absorption of light or moisture," from Old French incorporacion or directly from Late Latin incorporationem (nominative incorporatio) "an embodying, embodiment," noun of action from past-participle stem of incorporare "unite into one body" (see incorporate (v.)). Meaning "the formation of a corporate body (such as a guild) by the union of persons, forming an artificial person," is from early 15c.
Incorporation, n. The act of uniting several persons into one fiction called a corporation, in order that they may be no longer responsible for their actions. A, B and C are a corporation. A robs, B steals and C (it is necessary that there be one gentleman in the concern) cheats. It is a plundering, thieving, swindling corporation. But A, B and C, who have jointly determined and severally executed every crime of the corporation, are blameless. [Ambrose Bierce, 1885]