1610s, "bring into existence, make or cause to become real," also "exhibit the actual existence of," from French réaliser "make real" (16c.), from real "actual" (see real (adj.)). The sense of "understand clearly, comprehend the reality of" is recorded by 1775. Sense of "obtain, amass, bring or get into actual possession" (money, profit, etc.) is from 1753. Related: Realized; realizing.