The Biblical Elhanan was the son of Dodo (2 Samuel 23:24, 1 Chronicles 11:26). He was a member of King David’s elite fighters known as The Thirty.
Interpretation
Some, including Moshe Garsiel, believe he was in fact the same person as the Elhanan mentioned in 2 Samuel 21:19 and 1 Chronicles 20:5, the son of Jair from Bethlehem, and that the Bible is crediting him as the killer of Goliath. Garsiel concludes "that Elhanan is David’s previous name before he became king." Moreover, the Hebrew names David and Dodo are very similar, and were originally written without vowels as "DVD" and "DDV" respectively (דוד and דדו).
References
Elhanan son of Dodo Wikipedia(Text) CC BY-SA