It refers to a african's native tongue and how every other word sounds like woogie or boogie. When a white person uses it, they use it to mock. Same with ooga booga, or talking to Mr. and Mrs. Click Click Durk from west africa.
HEY! You niggers turn that music down! Niggers make me sick! WOOGIE BOOGIE NIGGER! WOOGIE BOOGIE! - Clayton, Black Klansmen