1. deserving praise, reward, esteem, etc.; praiseworthy: to receive a gift for meritorious service.
Origin: Meritorious is a good example of semantic amelioration. The Latin adjective meritōrius means “earning money, bringing in money, for hire.” Meritōrium is a noun use of this adjective and means “a room or place rented for a short time.” The plural of this noun meritōria means “house of prostitution, brothel.” Meritorious acquired a positive meaning in Middle English “entitling a person to a reward, especially a reward from God.” The word entered English in the first half of the 15th century.
“Not everything that is more difficult is more meritorious” - St. Thomas Aquinas