Onan was the second son of Judah. He refused to accept the obligation of marrying Tamar, who was the childless widow of his older brother, Er. According to the Hebrew laws of marriage, he was supposed to ensure Er's line by impregnating Tamar, and the children would legally become Er's children. But Onan declined this resposibility and "spilled his semen on the ground" to avoid contributing offspring for his brother. This offended the Lord, and the Lord took Onan's life. (Genesis 38:6-10). Onan means "power."
Next person in the Bible: Onesimus