late 14c., reflexion, in reference to surfaces throwing back light or heat, from Late Latin reflexionem (nominative reflexio) "a reflection," literally "a bending back," noun of action from past participle stem of Latin reflectere "to bend back, bend backwards, turn away," from re- "back" (see re-) + flectere "to bend" (see flexible). Of the mind, from 1670s. Meaning "remark made after turning back one's thought on some subject" is from 1640s. Spelling with -ct- recorded from late 14c., established 18c., by influence of the verb.