Only 2 batsmen have retired out in 140 years of Test cricket
The first-ever retired-out dismissal was witnessed when Marvan Atapattu was called in by Sanath Jayasuriya after scoring double ton in a Test against Bangladesh on September 7, 2001. In the same innings, Mahela Jaywardene also retired out after scoring 150. A batsman gets retired out when he retires for reasons other than injury or illness, and doesn't resume his innings.