Children of Ilúvatar
Men are also named the Apanónar ("Those born after" or "Afterborn"), Fírimar ("Mortals"), Engwar ("the Sickly"), and the Followers. These somewhat derogatory names were of course given to them by the Elves, who were the primary historians.
The reason for this naming is simple. Elves were the first of the Children of Ilúvatar to appear in Middle-earth, whereas Men were not to follow until the beginning of the First Age, with the creation of the Sun and Moon, many thousands of years later.