This was the name of three biblical men:
The first Er mentioned was a wicked man, the firstborn son of Judah. His mother was Shua the Canaanite (Genesis 38:2,4). His younger brother, Onan, was also wicked.
God put Er to death because of his wickedness (Genesis 38:7)
The second Er was relative of the first Er. He was a son of Shelah, the third son of Judah (1 Chronicles 4:21).
The third Er was a father who had a son named Elmodam. He was an ancestor in the named genealogy of Jesus Christ (Luke 3:28). He lived sometime between the time of King David and his descendant Zerubbabel.