merit (n.) Look up merit at Dictionary.com
c.1200, "spiritual credit" (for good works, etc.); c.1300, "spiritual reward," from Old French merite "wages, pay, reward; thanks; merit, moral worth, that which assures divine pity," and directly from Latin meritum "a merit, service, kindness, benefit, favor; worth, value, importance," neuter of meritus, past participle of merere, meriri "to earn, deserve, acquire, gain," from PIE root *(s)mer- "to allot, assign" (cognates: Greek meros "part, lot," moira "share, fate," moros "fate, destiny, doom," Hittite mark "to divide" a sacrifice).

Sense of "worthiness, excellence" is from early 14c.; from late 14c. as "condition or conduct that deserves either reward or punishment;" also "a reward, benefit." Related: Merits. Merit system attested from 1880. Merit-monger was in common use 16c.-17c. in a sense roughly of "do-gooder."
merit (v.) Look up merit at Dictionary.com
late 15c., "to be entitled to," from Middle French meriter (Modern French mériter), from merite (n.), or directly from Latin meritare "to earn, yield," frequentative of mereri "to earn (money);" also "to serve as a soldier" (see merit (n.)). Related: Merited; meriting.