The date of Ecthelion's birth appears only in The History of Middle-earth volume XII, The Peoples of Middle-earth. It cannot therefore be considered completely reliable.
2
It was common during this part of the Third Age for the Stewards to take their names from heroes of the First Age. Following this pattern, Steward Ecthelion I was doubtless named for Ecthelion of the Fountain, a famous Elf who dwelt in Gondolin. Tolkien gives two alternative origins for the name, at one point relating it to a word for 'fountain', but later to 'spear-point'. For more detail about the name's origins, see note 1 to the entry for Ecthelion of the Fountain.