Its root word is "likod" (back). Based on usage, "likuran" is used interchangeably with "likod", although strictly speaking, "likod" refers to the back itself, while "likuran" can mean the general area behind something.
"Makati ang likod/likuran ko" = My back is itchy. ("Likod" would be more accurate here)
"May kotse sa likod/likuran mo" = There's a car behind you ("Likuran" would be more accurate here)
"Kunan mo ng litrato si Beth na 'yung bundok ang nasa likod/likuran niya" = Take a picture of Beth with the mountain at the background. (Likuran)
"Ang dumi ng likod/likuran mo" = Your back is so dirty. (If the dirty part is only at the back of the torso, then "likod" would be accurate. However, if the dirty area is from the back of the head down to the heel, then "likuran" would be accurate)