Loc is also a shortened version of the word loco which means crazy.
Locs are also a popular sunglasses brand in California. They were originally worn by Cholos and are very popular with gangsters in the LA area. Locs have really dark tints which is one reason why they are so popular. Dr Dre referenced them in his song "Dre Day" in which he raps, "So strap on your Compton hat, your locs - And watch your back cause you might get smoked, loc."