What does John 1:47 mean?

Jesus' comment to Nathanael is mysterious; He labels him a "true Israelite," and notes his honesty. There are several ways to interpret Jesus' remark about Nathanael. All may apply at the same time. One possibility is that Jesus is making a blunt assessment of Nathanael, who in verse 46 certainly seemed willing to speak his mind. The second, more probable interpretation is that Christ was making a friendly joke. It's likely Jesus was teasing Nathanael, responding to sarcasm with sarcasm. Joking about a "true Israelite" having no deceit in him is a play on words. All Jewish people are descendants of Jacob, whom God renamed "Israel." Jacob would eventually become the father of the twelve men who founded the Twelve Tribes of Israel. Prior to his re-naming, Jacob was a habitual liar. He manipulated his brother in order to steal his birthright (Genesis 25:29–34). He tricked his father in order to steal his brother's firstborn blessing (Genesis 27). He was even born holding on to his twin brother's heel (Genesis 25:26). The name Jacob literally means, "Leg-puller," which meant much the same thing then as it does today. In verse 46, Nathanael had dismissed Jesus because He was from Nazareth. In response, Jesus' joke points out the mistake of judging a person based on heritage.