reflex (n.)youdaoicibaDictYouDict[reflex 词源字典]
c. 1500, "reflection of light," from verb reflex meaning "refract, deflect" (late 14c.), from Late Latin reflexus "a bending back," noun use of past participle of reflectere (see reflection). Meaning "involuntary nerve stimulation" first recorded 1877, from reflex action (1833).[reflex etymology, reflex origin, 英语词源]