Albert Barnes on John 9:36

Who is he? It is probable that the man did not know that ho who now addressed him was the same who had healed him. He had not yet seen him (Jn 9:7), but he was prepared to acknowledge him when he did see him. He inquired, therefore, who the person was, or wished that he might be pointed out to him, that he might see him. This passage shows that he was disposed to believe, and had a strong desire to see and hear the Son of God.

Lord. This word here, as in many other instances in the New Testament, means "Sir." It is clear that the man did not know that it was the Lord Jesus that addressed him, and he therefore replied to him in the common language of respect, and asked him to point out to him the Son of God. The word translated "Lord" here is rendered "Sir" in Jn 4:11 Jn 20:15, 12:21, Acts 16:30, Mt 27:63. It should have been also here, and in many other places.