Kommentar zu Divrej Hajamim I 20:5

And Elhanan the son of Jair smote He was one of David’s mighty men.

Lahmi, the brother of Goliath the Gittite, and the staff of his spear was as [thick as] a weavers’ beam like the round stick about which they wrap the cloth while weaving. Jonathan translated that verse in Samuel: And David the son of Jesse, the weaver of the dividing curtain of the Temple, slew. He interprets Jair (יָעִיר) as being similar to the Lebanon forest (יַעַר). He was paid in kind: Let David, whose mother wove the dividing curtain for the Temple with a weavers’ beam, slay Goliath, whose spear staff was as thick as a weavers’ beam. Now why does Scripture call him Elhanan? Because God favored him (ה' חֲנָנוֹ). I believe that Goliath the Gittite is not identical with Goliath the Philistine. One reason is that there [I Sam. 17:23] he called him Goliath the Philistine. Another reason is that above it is written: “... then Sibbecai the Hushathite smote Sippai of the sons of Rapha,” and also below it is written: “and he too was born to Raphah.” Since he does not mention that Goliath the Gittite was a son of Rapha, it proves that he [Goliath the Gittite] was not her son