What does 1 Samuel 17:55 mean?

And when Saul saw David go forth against the Philistine, he said unto Abner, the captain of the host, Abner, whose son is this youth? And Abner said, As thy soul liveth, O king, I cannot tell.

And when Saul saw David go forth against the Philistine, he said unto Abner, the captain of the host, Abner, whose son is this youth? And Abner said, As thy soul liveth, O king, I cannot tell.

And when Saul saw David go forth against the Philistine, he said unto Abner, the captain of the host, Abner, whose son is this youth? And Abner said, As thy soul liveth, O king, I cannot tell.

And when Saul saw David going out against the Philistine, he said to Abner, the captain of the army, Abner, whose son is this young man? And Abner said, On your life, O king, I have no idea.

And when Saul seeth David going out to meet the Philistine, he hath said unto Abner, head of the host, `Whose son <FI>is<Fi> this--the youth, Abner?' and Abner saith, `Thy soul liveth, O king, I have not known.'

Now at the time that Saul saw David going out against the Philistines, he said to Abner, the captain of the army: Of what family is this young man descended, Abner? And Abner said: As thy soul liveth, O king, I know not.

And when Saul saw David go forth against the Philistine, he said to Abner, the captain of the host, Abner, whose son is this young man? And Abner said, As thy soul liveth, O king, I cannot tell.