Elhanan son of Jair in Wikipedia

The biblical Elhanan son of Jair (variant forms "Jaare-Oregim" in 2 Samuel 21:19, "Jesse" in 1 Samuel 17:12) is believed by conservative Bible scholars to be an earlier name of David, who later became the second King of Israel. (See also Elhanan son of Dodo.) In the ancient world it was common for people to be known by one name at one time in their lives and to be known by another name or names at later times (see retroactive nomenclature). The name Elhanan is used in 2 Samuel 21:19 where he is mentioned as killing the Philistine giant Goliath and in 1 Chronicles 20:5, where in addition to Goliath he is also mentioned as killing Goliath’s brother Lahmi. The King James Version of the Bible adds the phrase "the brother of" before Goliath’s name, in order to avoid contradicting the better-known story that David killed the Philistine champion. The insertion is justified by a reference in Chronicles to Elhanan having killed Goliath’s brother. Other scholars assert that the omission of "brother of" in Samuel is likely to be a transcription error.[1]