Desmond Dekker encore! ... Dekker and the Aces recorded "A It Mek" in Jamaica in 1968, with the brass track added in the U.K. for the song's re-release in 1969, when the single ended up going to No. 7 on the U.K. Singles Chart. Before the end of 1970, it had sold more than a million copies worldwide. The title of the song is Jamaican patois for "That's Why" or "That's the Reason," though apparently the meaning is closer to "That's What You Get" (consequence being a recurring theme in ska and rocksteady). Can't say I've ever really figured out what the rest of the (mainly English) lyrics mean—the commenters on this blog have a good go—but always loved the connotation and color they bring to one of global popular music's great melodies.
From "swag" to "on fleek," tweens explain the changing English language.