leukocyte (n.) Look up leukocyte at Dictionary.com
also leucocyte, "white blood cell, white or colorless corpuscle of the blood or lymph," 1860, via French leucocyte, from leuco-, a Latinized comb. form of Greek leukos "white, clear," from PIE *leuk- "light, brightness" (see light (n.)) + -cyte "cell."