Onan

Strong, the second son of Judah (Gen. 38:4-10; comp. Deut. 25:5; Matt. 22:24). He died before the going down of Jacob and his family into Egypt.

(strong), the second son of Judah by the Canaanitess, “the daughter of Shua.” (Genesis 38:4; 1 Chronicles 2:3) “What he did was evil in the eyes of Jehovah and he slew him also, as he had slain his elder brother. (Genesis 38:9) His death took place before the family of Jacob went down into Egypt. (Genesis 46:12; Numbers 26:19) (B.C. 1706.)

o'-nan ('onan, "vigorous"; compare ONAM, a "son" of Judah (Ge 38:4,8-10; 46:12; Nu 26:19; 1Ch 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 Ge 38:11 Judah plainly attributes the death of his sons in some way to Tamar herself. The name is allied to Onam.