1350-1400;Middle English (< Old Frenchdesmerite) < Medieval Latindēmeritum fault, noun use of neuter past participle of Latindēmerēre to earn, win the favor of (dē- taken in ML as privative, hence pejorative). See de-, merit
1399, from O.Fr. desmerite, from des- "not, opposite" + merite "merit." L. demereri meant "to merit, deserve," from de- in its completive sense. But M.L. demeritum meant "fault." Both senses existed in the M.Fr. form of the word. Meaning "penalty point in school" is attested from 1862.