In December 2011, the group finalized their name to EXO, with the names EXO-K for the South Korean subgroup and EXO-M for the Chinese subgroup. Their name was taken from the word exoplanet.[16] The twelve members were introduced individually through 23 different trailers released from December 2011 to February 2012.[16][17] Kai, Lu Han, Tao, and Chen were the first four members introduced, and they debuted their first televised performance at SBS's annual Gayo Daejun event on December 29, 2011.[18]
EXO-K and EXO-M's prologue single "What Is Love" was released on January 30, 2012, in mainland China and South Korea.[19] The single peaked at number 88 on South Korea's Gaon Single Chart. On March 9, the group released their second prologue single "History",[20] which was written and produced by Thomas Troelsen and Remee. The single peaked at number 68 on the Gaon Single Chart and number six on China's Sina Music Chart.[21]
A concert for the group was held in Seoul's Olympic Stadium on March 31.[22]