Easton's Bible Dictionary Strong, the second son of Judah (Genesis 38:4-10; Comp. Deuteronomy 25:5; Matthew 22:24). He died before the going down of Jacob and his family into Egypt. Int. Standard Bible Encyclopedia ONAN o'-nan ('onan, "vigorous"; compare ONAM, a "son" of Judah (Genesis 38:4, 8-10; Genesis 46:12 Numbers 26:19 1 Chronicles 2:3); "The story of the untimely death of Er and Onan implies that two of the ancient clans of Judah early disappeared" (Curtis, Chron, 84). See Skinner, Gen, 452, where it is pointed out that in Genesis 38:11 Judah plainly attributes the death of his sons in some way to Tamar herself. The name is allied to Onam.

Multi-Version Concordance Onan (6 Occurrences) Genesis 38:4 She conceived again, and bore a son; and she named him Onan. (WEB KJV JPS ASV BBE DBY WBS YLT NAS RSV NIV) Genesis 38:8 Judah said to Onan, "Go in to your brother's wife, and perform the duty of a husband's brother to her, and raise up seed to your brother." (WEB KJV JPS ASV BBE DBY WBS YLT NAS RSV NIV) Genesis 38:9 Onan knew that the seed wouldn't be his; and it happened, when he went in to his brother's wife, that he spilled it on the ground, lest he should give seed to his brother. (WEB KJV JPS ASV BBE DBY WBS YLT NAS RSV NIV) Genesis 46:12 The sons of Judah: Er, Onan, Shelah, Perez, and Zerah; but Er and Onan died in the land of Canaan. The sons of Perez were Hezron and Hamul. (WEB KJV JPS ASV BBE DBY WBS YLT NAS RSV NIV) Numbers 26:19 The sons of Judah: Er and Onan; and Er and Onan died in the land of Canaan. (WEB KJV JPS ASV BBE DBY WBS YLT NAS RSV NIV) 1 Chronicles 2:3 The sons of Judah: Er, and Onan, and Shelah; which three were born to him of Shua's daughter the Canaanitess. Er, Judah's firstborn, was wicked in the sight of Yahweh; and he killed him. (WEB KJV JPS ASV BBE DBY WBS YLT NAS RSV NIV)